[mail/checkmail.git] / checkmail.pl

#! /usr/bin/perl -W
#
# checkmail Version 0.3 by Thomas Hochstein
#
# This script tries to verify the deliverability of (a) mail address(es).
# 
# Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>
#
# It can be redistributed and/or modified under the same terms under 
# which Perl itself is published.

our $VERSION = "0.3";

################################# Configuration ################################
# Please fill in a working configuration!
my %config=(
            # value used for HELO/EHLO - a valid hostname you own
            helo => 'testhost.domain.example',
            # value used for MAIL FROM: - a valid address under your control
            from => 'mailtest@testhost.domain.example',
            # a syntactically valid "random" - reliably not existing - localpart
            rand => 'ZOq62fow1i'
           );

################################### Modules ####################################
use strict;
use File::Basename;
use Getopt::Std;
use Net::DNS;
use Net::SMTP;

################################# Main program #################################

$Getopt::Std::STANDARD_HELP_VERSION = 1;
my $myself = basename($0);

# read commandline options
my %options;
getopts('Vhqlrf:m:', \%options);

# -V: display version
if ($options{'V'}) {
  print "$myself v $VERSION\nCopyright (c) 2010 Thomas Hochstein <thh\@inter.net>\n";
  print "This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.\n";
  exit(100);
};

# -h: feed myself to perldoc
if ($options{'h'}) {
  exec('perldoc', $0);
  exit(100);
};

# display usage information if neither -f nor an address are present
if (!$options{'f'} and !$ARGV[0]) {
  print "Usage: $myself [-hqlr] [-m <host>] <address>|-f <file>\n";
  print "Options: -V  display copyright and version\n";
  print "         -h  show documentation\n";
  print "         -q  quiet (no output, just exit with 0/1/2/3)\n";
  print "         -l  extended logging\n";
  print "         -r  test random address to verify verification\n";
  print "  -m <host>  no DNS lookup, just test this host\n";
  print "  <address>  mail address to check\n\n";
  print "  -f <file>  parse file (one address per line)\n";
  exit(100);
};

# -f: open file and read addresses to @adresses
my @addresses;
if ($options{'f'}) {
 if (-e $options{'f'}) {
  open FILE, "<$options{'f'}" or die("$myself ERROR: Could not open file $options{'f'} for reading: $!");
 } else {
  die("$myself ERROR: File $options{'f'} does not exist!\n");
 };
 while(<FILE>) {
  chomp;
  push(@addresses,$_);
 };
 close FILE;
# fill @adresses with single address to check
 } else {
  push(@addresses,$ARGV[0]);
};

# loop over each address and test it
my (%targets,$curstat,$status,$log,$message);
foreach (@addresses) {
  my $address = $_;
  (undef,my $domain) = splitaddress($address);
  printf("  * Testing %s ...\n",$address) if !($options{'q'});
  $log .=  "\n===== BEGIN $address =====\n";
  # get list of target hosts or take host forced via -m
  if (!$options{'m'}) {
	  %targets = %{gettargets($domain,\$log)};
  } else {
    $message = sprintf("Connection to %s forced by -m.\n",$options{'m'});
    $log .= $message;
    print "    $message" if !($options{'q'});
    # just one target host with preference 0
    $targets{$options{'m'}} = 0;
  };
  if (%targets) {
    $curstat = checkaddress($address,\%targets,\$log);
  } else {
    $curstat = 2;
    $message = 'DNS lookup failure';
    printf("  > Address is INVALID (%s).\n",$message) if !($options{'q'});
    $log .= $message . '.';
  };
  $log   .=  "====== END $address ======\n";
  $status = $curstat if (!defined($status) or $curstat > $status);
};

print $log if ($options{'l'});

# status 0: valid / batch processing
#        1: connection failed or temporary failure
#        2: invalid
#        3: cannot verify
#D print "\n-> EXIT $status\n";
exit($status);

################################## gettargets ##################################
# get mail exchanger(s) or A record(s) for a domain
# IN : $domain: domain to query the DNS for
# OUT: \%targets: reference to a hash containing a list of target hosts
sub gettargets {
  my ($domain,$logr) = @_;
  # resolver objekt
  my $resolver = Net::DNS::Resolver->new(udp_timeout => 15, tcp_timeout => 15);

  my %targets;
  # get MX record(s) as a list sorted by preference
  if (my @mxrr = mx($resolver,$domain)) {
    print_dns_result($domain,'MX',scalar(@mxrr),undef,$logr);
    foreach my $rr (@mxrr) {
	 $targets{$rr->exchange} = $rr->preference;
	 $$logr .= sprintf("(%d) %s\n",$rr->preference,$rr->exchange);
    };
  # no MX record found; log and try A record(s)
  } else {
    print_dns_result($domain,'MX',undef,$resolver->errorstring,$logr);
    print("    Falling back to A record ...\n") if !($options{'q'});
	# get A record(s)
    if (my $query = $resolver->query($domain,'A','IN')) {
      print_dns_result($domain,'A',$query->header->ancount,undef,$logr);
      foreach my $rr ($query->answer) {
        $targets{$rr->address} = 0;
        $$logr .= sprintf("- %s\n",$rr->address);
      };
    # no A record found either; log and fail
    } else {
      print_dns_result($domain,'A',undef,$resolver->errorstring,$logr);
      printf("    %s has neither MX nor A records - mail cannot be delivered.\n",$domain) if !($options{'q'});
    };
  };
  return \%targets;
};

################################# checkaddress #################################
# test address for deliverability
# IN : $address: adress to be tested
#      \%targets: reference to a hash containing a list of MX hosts
#      \$log    : reference to the log (to be printed out via -l)
# OUT: ---
#      \$log will be changed
sub checkaddress {
  my ($address,$targetsr,$logr) = @_;
  my %targets = %{$targetsr};
  my $status;
  # walk %targets in order of preference
  foreach my $host (sort { $targets{$a} <=> $targets{$b} } keys %targets) {
    printf("  / Trying %s (%s) with %s\n",$host,$targets{$host} || 'A',$address) if !($options{'q'});
	  $$logr .= sprintf("%s:\n%s\n",$host,"-" x (length($host)+1));
	  $status = checksmtp($address,$host,$logr);
	  last if ($status != 1);
  };
  return $status;
};

################################### checksmtp ##################################
# connect to a remote machine on port 25 and test deliverability of a mail
# address by doing the SMTP dialog until RCPT TO stage
# IN : $address: address to test
#      $target : target host
#      \$log    : reference to the log (to be printed out via -l)
# OUT: .........: reference to a hash containing a list of target hosts
#      \$log will be changed
sub checksmtp {
  my ($address,$target,$logr) = @_;
  my ($status);
  # start SMTP connection
  if (my $smtp = Net::SMTP->new($target,Hello => $config{'helo'},Timeout => 30)) {
    $$logr .= $smtp->banner; # Net::SMTP doesn't seem to support multiline greetings.
    $$logr .= "EHLO $config{'helo'}\n";
    log_smtp_reply($logr,$smtp->code,$smtp->message);
    $smtp->mail($config{'from'});
    $$logr .= "MAIL FROM:<$config{'from'}>\n";
    log_smtp_reply($logr,$smtp->code,$smtp->message);
    # test address
    my ($success,$code,@message) = try_rcpt_to(\$smtp,$address,$logr);
    # connection failure?
    if ($success < 0) {
      $status = connection_failed(@message);
    # delivery attempt was successful?
    } elsif ($success) {
      # -r: try random address (which should be guaranteed to be invalid)
      if ($options{'r'}) {
        (undef,my $domain) = splitaddress($address);
        my ($success,$code,@message) = try_rcpt_to(\$smtp,$config{'rand'}.'@'.$domain,$logr);
        # connection failure?
        if ($success < 0) {
          $status = connection_failed(@message);
        # verification impossible?
        } elsif ($success) {
          $status = 3;
          print "  > Address verificaton impossible. You'll have to send a test mail ...\n" if !($options{'q'});
        }
      }
      # if -r is not set or status was not set to 3: valid address
      if (!defined($status)) {
        $status = 0;
        print "  > Address is valid.\n" if !($options{'q'});
      };
    # delivery attempt failed?
    } else {
      $status = 2;
      print "  > Address is INVALID:\n" if !($options{'q'});
      print '    ' . join('    ',@message) if !($options{'q'});
    }
    # terminate SMTP connection
    $smtp->quit;
    $$logr .= "QUIT\n";
    log_smtp_reply($logr,$smtp->code,$smtp->message);
  } else {
    # SMTP connection failed / timeout
    $status = connection_failed();
    $$logr .= "---Connection failure---\n";
  };
  return $status;
}

################################# splitaddress #################################
# split mail address into local and domain part
# IN : $address: a mail address
# OUT: $local : local part
#      $domain: domain part
sub splitaddress {
  my($address)=@_;
  (my $lp = $address) =~ s/^([^@]+)@.*/$1/;
  (my $domain = $address) =~ s/[^@]+\@(\S*)$/$1/;
  return ($lp,$domain);
};

################################ parse_dns_reply ###############################
# parse DNS response codes and return code and description
# IN : $response: a DNS response code
# OUT: "$response ($desciption)"
sub parse_dns_reply {
  my($response)=@_;
  my %dnsrespcodes = (NOERROR  => 'empty response',
                      NXDOMAIN => 'non-existent domain',
                      SERVFAIL => 'DNS server failure',
                      REFUSED  => 'DNS query refused',
                      FORMERR  => 'format error',
                      NOTIMP   => 'not implemented');
  if(defined($dnsrespcodes{$response})) {
    return sprintf('%s (%s)',$response,$dnsrespcodes{$response});
  } else {
    return $response;
  };
};

############################### print_dns_result ###############################
# print and log result of DNS query
# IN : $domain: domain the DNS was queried for
#      $type  : record type (MX, A, ...)
#      $count : number of records found
#      $error : DNS response code
#      \$log : reference to the log (to be printed out via -l)
# OUT: ---
#      \$log will be changed
sub print_dns_result {
  my ($domain,$type,$count,$error,$logr) = @_;
  if (defined($count)) {
    printf("    %d %s record(s) found for %s\n",$count,$type,$domain) if !($options{'q'});
    $$logr .= sprintf("%s DNS record(s):\n",$type);
  } else {
    printf("    No %s records found for %s: %s\n",$type,$domain,parse_dns_reply($error)) if !($options{'q'});
    $$logr .= sprintf("No %s records found: %s\n",$type,parse_dns_reply($error));
  };
  return;
};

################################## try_rcpt_to #################################
# send RCPT TO and return replies
# IN : \$smtp    : a reference to an SMTP object
#      $recipient: a mail address
#      \$log     : reference to the log (to be printed out via -l)
# OUT: $success: exit code (0 for false, 1 for true, -1 for tempfail)
#      $code   : SMTP status code
#      $message: SMTP status message
#      \$log will be changed
sub try_rcpt_to {
  my($smtpr,$recipient,$logr)=@_;
  $$logr .= sprintf("RCPT TO:<%s>\n",$recipient);
  my $success;
  $$smtpr->to($recipient);
  if ($$smtpr->code) {
    log_smtp_reply($logr,$$smtpr->code,$$smtpr->message);
    $success = analyze_smtp_reply($$smtpr->code,$$smtpr->message);
  } else {
    $success = -1;
    $$logr .= "---Connection failure---\n";
  };
  return ($success,$$smtpr->code,$$smtpr->message);
};

################################ log_smtp_reply ################################
# log result of SMTP command
# IN : \$log    : reference to the log (to be printed out via -l)
#      $code    : SMTP status code
#      @message : SMTP status message
# OUT: ---
#      \$log will be changed
sub log_smtp_reply {
  my($logr,$code,@message)=@_;
  $$logr .= sprintf('%s %s',$code,join('- ',@message));
  return;
}

############################### analyze_smtp_reply ##############################
# analyze SMTP response codes and messages
# IN : $code    : SMTP status code
#      @message : SMTP status message
# OUT: exit code (0 for false, 1 for true, -1 for tempfail)
sub analyze_smtp_reply {
  my($code,@message)=@_;
  my $type = substr($code, 0, 1);
  if ($type == 2) {
    return 1;
  } elsif ($type == 5) {
    return 0;
  } elsif ($type == 4) {
    return -1;
  };
  return -1;
}

############################## connection_failed ###############################
# print failure message and return status 1
# IN : @message : SMTP status message
# OUT: 1
sub connection_failed {
  my(@message)=@_;
  print "  ! Connection failed or other temporary failure.\n" if !($options{'q'});
  printf("    %s\n",join('    ',@message)) if @message;
  return 1;
}

__END__

################################ Documentation #################################

=head1 NAME

checkmail - check deliverability of a mail address

=head1 SYNOPSIS

B<checkmail> [B<-Vhqlr>] [B<-m> I<host>] I<address>|B<-f> I<file>

=head1 REQUIREMENTS

=over 2

=item -

Perl 5.8 or later

=item -

File::Basename

=item -

Getopt::Std

=item -

Net::DNS I<(CPAN)>

=item -

Net::SMTP

=back

Furthermore you'll need a working DNS installation.

=head1 DESCRIPTION

checkmail checks the vailidity / deliverability of a mail address.
You may submit just one address as the last argument or a file
containing one address on each line using the B<-f> option.

=head2 Configuration

For the time being, all configuration is done in the script. You have
to set the following elements of the %config hash:

=over 4

=item B<$config{'helo'}>

The hostname to be used for I<HELO> or I<EHLO> in the SMTP dialog.

=item B<$config{'from'}>

The sender address to be used for I<MAIL FROM> while testing.

=item B<$config{'rand'}>

A "random" local part to construct a reliably invalid address for use
with the B<-r> option.

=back

=head2 Usage

After configuring the script you may run your first test with

    checkmail user@example.org

B<checkmail> will try to determine the mail exchanger(s) (MX)
responsible for I<example.org> by querying the DNS for the respective
MX records and then try to connect via SMTP (on port 25) to each of
them in order of precedence (if necessary). It will run through the
SMTP dialog until just before the I<DATA> stage, i.e. doing I<EHLO>,
I<MAIL FROM> and I<RCPT TO>. If no MX is defined, B<checkmail> will
fall back to the I<example.org> host itself, provided there is at
least one A record defined in the DNS. If there are neither MX nor A
records for I<example.org>, mail is not deliverable and B<checkmail>
will fail accordingly. If no host can be reached, B<checkmail> will
fail, too. Finally B<checkmail> will fail if mail to the given
recipient is not accepted by the respective host.

If B<checkmail> fails, you'll not be able to deliver mail to that
address - at least not using the configured sender address and from
the host you're testing from. However, the opposite is not true: a
mail you send may still not be delivered even if a test via
B<checkmail> succeeds. The receiving entity may reject your mail after
the I<DATA> stage, due to content checking or without any special
reason, or it may even drop, filter or bounce your mail after finally
accepting it. There is no way to be sure a mail will be accepted short
of sending a real mail to the address in question.

You may, however, try to detect hosts that will happily accept any and
all recipient in the SMTP dialog and just reject your mail later on,
for example to defeat exactly the kind of check you try to do.
B<checkmail> will do that by submitting a recipient address that is
known to be invalid; if that address is accepted, too, you'll know
that you can't reliably check the validity of any address on that
host. You can force that check by using the B<-r> option.

If you don't want to see just the results of your test, you can get a
B<complete log> of the SMTP dialog by using the B<-l> option. That may be
helpful to test for temporary failure conditions.

On the other hand you may use the B<-q> option to suppress all output;
B<checkmail> will then terminate with one of the following B<exit
status>:
       
=over 4

=item B<0>

address(es) seem/seems to be valid

=item B<1>

temporary error (connection failure or temporary failure)

=item B<2>

address is invalid

=item B<3>

address cannot reliably be checked (test using B<-r> failed)

=back

You can do B<batch processing> using B<-f> and submitting a file with
one address on each line. In that case the exit status is set to the
highest value generated by testing all addresses, i.e. it is set to
B<0> if and only if no adress failed, but to B<2> if even one address
failed and to B<3> if even one addresses couldn't reliably be checked.

And finally you can B<suppress DNS lookups> for MX and A records and
just force B<checkmail> to connect to a particular host using the
B<-m> option.

B<Please note:> You shouldn't try to validate addresses while working
from a dial-up or blacklisted host. If in doubt, use the B<-l> option
to have a closer look on the SMTP dialog yourself.

=head1 OPTIONS

=over 3

=item B<-V> (version)

Print out version and copyright information on B<checkmail> and exit.

=item B<-h> (help)

Print this man page and exit.

=item B<-q> (quit)

Suppress output and just terminate with a specific exit status.

=item B<-l> (log)

Log and print out the whole SMTP dialog.

=item B<-r> (random address)

Also try a reliably invalid address - defined in B<$config{'rand'}> -
to catch hosts that try undermine address verification.

=item B<-m> I<host> (MX to use)

Force a connection to I<host> to check deliverability to that
particular host irrespective of DNS entries. For example:

    checkmail -m test.host.example user@domain.example

=item B<-f> I<file> (file)

Process all addresses from I<file> (one on each line).

=back

=head1 INSTALLATION

Just copy checkmail to some directory and get started.

You can run your first test with

    checkmail user@example.org

=head1 ENVIRONMENT

See documentation of I<Net::DNS::Resolver>.

=head1 FILES

=over 4

=item F<checkmail.pl>

The script itself.

=back

=head1 BUGS

Please report any bugs or feature request to the author or use the
bug tracker at L<http://bugs.th-h.de/>!

=head1 SEE ALSO

L<http://th-h.de/download/scripts.php> will have the current
version of this program.

This program is maintained using the Git version control system. You
may clone L<git://code.th-h.de/mail/checkmail.git> to check out the
current development tree or browse it on the web via
L<http://code.th-h.de/?p=mail/checkmail.git>.

=head1 AUTHOR

Thomas Hochstein <thh@inter.net>

=head1 COPYRIGHT AND LICENSE

Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>

This program is free software; you may redistribute it and/or modify it
under the same terms as Perl itself.

=cut
Commit	Line	Data
	1	#! /usr/bin/perl -W
	2	#
	3	# checkmail Version 0.3 by Thomas Hochstein
	4	#
	5	# This script tries to verify the deliverability of (a) mail address(es).
	6	#
	7	# Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>
	8	#
	9	# It can be redistributed and/or modified under the same terms under
	10	# which Perl itself is published.
	11
	12	our $VERSION = "0.3";
	13
	14	################################# Configuration ################################
	15	# Please fill in a working configuration!
	16	my %config=(
	17	# value used for HELO/EHLO - a valid hostname you own
	18	helo => 'testhost.domain.example',
	19	# value used for MAIL FROM: - a valid address under your control
	20	from => 'mailtest@testhost.domain.example',
	21	# a syntactically valid "random" - reliably not existing - localpart
	22	rand => 'ZOq62fow1i'
	23	);
	24
	25	################################### Modules ####################################
	26	use strict;
	27	use File::Basename;
	28	use Getopt::Std;
	29	use Net::DNS;
	30	use Net::SMTP;
	31
	32	################################# Main program #################################
	33
	34	$Getopt::Std::STANDARD_HELP_VERSION = 1;
	35	my $myself = basename($0);
	36
	37	# read commandline options
	38	my %options;
	39	getopts('Vhqlrf:m:', \%options);
	40
	41	# -V: display version
	42	if ($options{'V'}) {
	43	print "$myself v $VERSION\nCopyright (c) 2010 Thomas Hochstein <thh\@inter.net>\n";
	44	print "This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.\n";
	45	exit(100);
	46	};
	47
	48	# -h: feed myself to perldoc
	49	if ($options{'h'}) {
	50	exec('perldoc', $0);
	51	exit(100);
	52	};
	53
	54	# display usage information if neither -f nor an address are present
	55	if (!$options{'f'} and !$ARGV[0]) {
	56	print "Usage: $myself [-hqlr] [-m <host>] <address>\|-f <file>\n";
	57	print "Options: -V display copyright and version\n";
	58	print " -h show documentation\n";
	59	print " -q quiet (no output, just exit with 0/1/2/3)\n";
	60	print " -l extended logging\n";
	61	print " -r test random address to verify verification\n";
	62	print " -m <host> no DNS lookup, just test this host\n";
	63	print " <address> mail address to check\n\n";
	64	print " -f <file> parse file (one address per line)\n";
	65	exit(100);
	66	};
	67
	68	# -f: open file and read addresses to @adresses
	69	my @addresses;
	70	if ($options{'f'}) {
	71	if (-e $options{'f'}) {
	72	open FILE, "<$options{'f'}" or die("$myself ERROR: Could not open file $options{'f'} for reading: $!");
	73	} else {
	74	die("$myself ERROR: File $options{'f'} does not exist!\n");
	75	};
	76	while(<FILE>) {
	77	chomp;
	78	push(@addresses,$_);
	79	};
	80	close FILE;
	81	# fill @adresses with single address to check
	82	} else {
	83	push(@addresses,$ARGV[0]);
	84	};
	85
	86	# loop over each address and test it
	87	my (%targets,$curstat,$status,$log,$message);
	88	foreach (@addresses) {
	89	my $address = $_;
	90	(undef,my $domain) = splitaddress($address);
	91	printf(" * Testing %s ...\n",$address) if !($options{'q'});
	92	$log .= "\n===== BEGIN $address =====\n";
	93	# get list of target hosts or take host forced via -m
	94	if (!$options{'m'}) {
	95	%targets = %{gettargets($domain,\$log)};
	96	} else {
	97	$message = sprintf("Connection to %s forced by -m.\n",$options{'m'});
	98	$log .= $message;
	99	print " $message" if !($options{'q'});
	100	# just one target host with preference 0
	101	$targets{$options{'m'}} = 0;
	102	};
	103	if (%targets) {
	104	$curstat = checkaddress($address,\%targets,\$log);
	105	} else {
	106	$curstat = 2;
	107	$message = 'DNS lookup failure';
	108	printf(" > Address is INVALID (%s).\n",$message) if !($options{'q'});
	109	$log .= $message . '.';
	110	};
	111	$log .= "====== END $address ======\n";
	112	$status = $curstat if (!defined($status) or $curstat > $status);
	113	};
	114
	115	print $log if ($options{'l'});
	116
	117	# status 0: valid / batch processing
	118	# 1: connection failed or temporary failure
	119	# 2: invalid
	120	# 3: cannot verify
	121	#D print "\n-> EXIT $status\n";
	122	exit($status);
	123
	124	################################## gettargets ##################################
	125	# get mail exchanger(s) or A record(s) for a domain
	126	# IN : $domain: domain to query the DNS for
	127	# OUT: \%targets: reference to a hash containing a list of target hosts
	128	sub gettargets {
	129	my ($domain,$logr) = @_;
	130	# resolver objekt
	131	my $resolver = Net::DNS::Resolver->new(udp_timeout => 15, tcp_timeout => 15);
	132
	133	my %targets;
	134	# get MX record(s) as a list sorted by preference
	135	if (my @mxrr = mx($resolver,$domain)) {
	136	print_dns_result($domain,'MX',scalar(@mxrr),undef,$logr);
	137	foreach my $rr (@mxrr) {
	138	$targets{$rr->exchange} = $rr->preference;
	139	$$logr .= sprintf("(%d) %s\n",$rr->preference,$rr->exchange);
	140	};
	141	# no MX record found; log and try A record(s)
	142	} else {
	143	print_dns_result($domain,'MX',undef,$resolver->errorstring,$logr);
	144	print(" Falling back to A record ...\n") if !($options{'q'});
	145	# get A record(s)
	146	if (my $query = $resolver->query($domain,'A','IN')) {
	147	print_dns_result($domain,'A',$query->header->ancount,undef,$logr);
	148	foreach my $rr ($query->answer) {
	149	$targets{$rr->address} = 0;
	150	$$logr .= sprintf("- %s\n",$rr->address);
	151	};
	152	# no A record found either; log and fail
	153	} else {
	154	print_dns_result($domain,'A',undef,$resolver->errorstring,$logr);
	155	printf(" %s has neither MX nor A records - mail cannot be delivered.\n",$domain) if !($options{'q'});
	156	};
	157	};
	158	return \%targets;
	159	};
	160
	161	################################# checkaddress #################################
	162	# test address for deliverability
	163	# IN : $address: adress to be tested
	164	# \%targets: reference to a hash containing a list of MX hosts
	165	# \$log : reference to the log (to be printed out via -l)
	166	# OUT: ---
	167	# \$log will be changed
	168	sub checkaddress {
	169	my ($address,$targetsr,$logr) = @_;
	170	my %targets = %{$targetsr};
	171	my $status;
	172	# walk %targets in order of preference
	173	foreach my $host (sort { $targets{$a} <=> $targets{$b} } keys %targets) {
	174	printf(" / Trying %s (%s) with %s\n",$host,$targets{$host} \|\| 'A',$address) if !($options{'q'});
	175	$$logr .= sprintf("%s:\n%s\n",$host,"-" x (length($host)+1));
	176	$status = checksmtp($address,$host,$logr);
	177	last if ($status != 1);
	178	};
	179	return $status;
	180	};
	181
	182	################################### checksmtp ##################################
	183	# connect to a remote machine on port 25 and test deliverability of a mail
	184	# address by doing the SMTP dialog until RCPT TO stage
	185	# IN : $address: address to test
	186	# $target : target host
	187	# \$log : reference to the log (to be printed out via -l)
	188	# OUT: .........: reference to a hash containing a list of target hosts
	189	# \$log will be changed
	190	sub checksmtp {
	191	my ($address,$target,$logr) = @_;
	192	my ($status);
	193	# start SMTP connection
	194	if (my $smtp = Net::SMTP->new($target,Hello => $config{'helo'},Timeout => 30)) {
	195	$$logr .= $smtp->banner; # Net::SMTP doesn't seem to support multiline greetings.
	196	$$logr .= "EHLO $config{'helo'}\n";
	197	log_smtp_reply($logr,$smtp->code,$smtp->message);
	198	$smtp->mail($config{'from'});
	199	$$logr .= "MAIL FROM:<$config{'from'}>\n";
	200	log_smtp_reply($logr,$smtp->code,$smtp->message);
	201	# test address
	202	my ($success,$code,@message) = try_rcpt_to(\$smtp,$address,$logr);
	203	# connection failure?
	204	if ($success < 0) {
	205	$status = connection_failed(@message);
	206	# delivery attempt was successful?
	207	} elsif ($success) {
	208	# -r: try random address (which should be guaranteed to be invalid)
	209	if ($options{'r'}) {
	210	(undef,my $domain) = splitaddress($address);
	211	my ($success,$code,@message) = try_rcpt_to(\$smtp,$config{'rand'}.'@'.$domain,$logr);
	212	# connection failure?
	213	if ($success < 0) {
	214	$status = connection_failed(@message);
	215	# verification impossible?
	216	} elsif ($success) {
	217	$status = 3;
	218	print " > Address verificaton impossible. You'll have to send a test mail ...\n" if !($options{'q'});
	219	}
	220	}
	221	# if -r is not set or status was not set to 3: valid address
	222	if (!defined($status)) {
	223	$status = 0;
	224	print " > Address is valid.\n" if !($options{'q'});
	225	};
	226	# delivery attempt failed?
	227	} else {
	228	$status = 2;
	229	print " > Address is INVALID:\n" if !($options{'q'});
	230	print ' ' . join(' ',@message) if !($options{'q'});
	231	}
	232	# terminate SMTP connection
	233	$smtp->quit;
	234	$$logr .= "QUIT\n";
	235	log_smtp_reply($logr,$smtp->code,$smtp->message);
	236	} else {
	237	# SMTP connection failed / timeout
	238	$status = connection_failed();
	239	$$logr .= "---Connection failure---\n";
	240	};
	241	return $status;
	242	}
	243
	244	################################# splitaddress #################################
	245	# split mail address into local and domain part
	246	# IN : $address: a mail address
	247	# OUT: $local : local part
	248	# $domain: domain part
	249	sub splitaddress {
	250	my($address)=@_;
	251	(my $lp = $address) =~ s/^([^@]+)@.*/$1/;
	252	(my $domain = $address) =~ s/[^@]+\@(\S*)$/$1/;
	253	return ($lp,$domain);
	254	};
	255
	256	################################ parse_dns_reply ###############################
	257	# parse DNS response codes and return code and description
	258	# IN : $response: a DNS response code
	259	# OUT: "$response ($desciption)"
	260	sub parse_dns_reply {
	261	my($response)=@_;
	262	my %dnsrespcodes = (NOERROR => 'empty response',
	263	NXDOMAIN => 'non-existent domain',
	264	SERVFAIL => 'DNS server failure',
	265	REFUSED => 'DNS query refused',
	266	FORMERR => 'format error',
	267	NOTIMP => 'not implemented');
	268	if(defined($dnsrespcodes{$response})) {
	269	return sprintf('%s (%s)',$response,$dnsrespcodes{$response});
	270	} else {
	271	return $response;
	272	};
	273	};
	274
	275	############################### print_dns_result ###############################
	276	# print and log result of DNS query
	277	# IN : $domain: domain the DNS was queried for
	278	# $type : record type (MX, A, ...)
	279	# $count : number of records found
	280	# $error : DNS response code
	281	# \$log : reference to the log (to be printed out via -l)
	282	# OUT: ---
	283	# \$log will be changed
	284	sub print_dns_result {
	285	my ($domain,$type,$count,$error,$logr) = @_;
	286	if (defined($count)) {
	287	printf(" %d %s record(s) found for %s\n",$count,$type,$domain) if !($options{'q'});
	288	$$logr .= sprintf("%s DNS record(s):\n",$type);
	289	} else {
	290	printf(" No %s records found for %s: %s\n",$type,$domain,parse_dns_reply($error)) if !($options{'q'});
	291	$$logr .= sprintf("No %s records found: %s\n",$type,parse_dns_reply($error));
	292	};
	293	return;
	294	};
	295
	296	################################## try_rcpt_to #################################
	297	# send RCPT TO and return replies
	298	# IN : \$smtp : a reference to an SMTP object
	299	# $recipient: a mail address
	300	# \$log : reference to the log (to be printed out via -l)
	301	# OUT: $success: exit code (0 for false, 1 for true, -1 for tempfail)
	302	# $code : SMTP status code
	303	# $message: SMTP status message
	304	# \$log will be changed
	305	sub try_rcpt_to {
	306	my($smtpr,$recipient,$logr)=@_;
	307	$$logr .= sprintf("RCPT TO:<%s>\n",$recipient);
	308	my $success;
	309	$$smtpr->to($recipient);
	310	if ($$smtpr->code) {
	311	log_smtp_reply($logr,$$smtpr->code,$$smtpr->message);
	312	$success = analyze_smtp_reply($$smtpr->code,$$smtpr->message);
	313	} else {
	314	$success = -1;
	315	$$logr .= "---Connection failure---\n";
	316	};
	317	return ($success,$$smtpr->code,$$smtpr->message);
	318	};
	319
	320	################################ log_smtp_reply ################################
	321	# log result of SMTP command
	322	# IN : \$log : reference to the log (to be printed out via -l)
	323	# $code : SMTP status code
	324	# @message : SMTP status message
	325	# OUT: ---
	326	# \$log will be changed
	327	sub log_smtp_reply {
	328	my($logr,$code,@message)=@_;
	329	$$logr .= sprintf('%s %s',$code,join('- ',@message));
	330	return;
	331	}
	332
	333	############################### analyze_smtp_reply ##############################
	334	# analyze SMTP response codes and messages
	335	# IN : $code : SMTP status code
	336	# @message : SMTP status message
	337	# OUT: exit code (0 for false, 1 for true, -1 for tempfail)
	338	sub analyze_smtp_reply {
	339	my($code,@message)=@_;
	340	my $type = substr($code, 0, 1);
	341	if ($type == 2) {
	342	return 1;
	343	} elsif ($type == 5) {
	344	return 0;
	345	} elsif ($type == 4) {
	346	return -1;
	347	};
	348	return -1;
	349	}
	350
	351	############################## connection_failed ###############################
	352	# print failure message and return status 1
	353	# IN : @message : SMTP status message
	354	# OUT: 1
	355	sub connection_failed {
	356	my(@message)=@_;
	357	print " ! Connection failed or other temporary failure.\n" if !($options{'q'});
	358	printf(" %s\n",join(' ',@message)) if @message;
	359	return 1;
	360	}
	361
	362	__END__
	363
	364	################################ Documentation #################################
	365
	366	=head1 NAME
	367
	368	checkmail - check deliverability of a mail address
	369
	370	=head1 SYNOPSIS
	371
	372	B<checkmail> [B<-Vhqlr>] [B<-m> I<host>] I<address>\|B<-f> I<file>
	373
	374	=head1 REQUIREMENTS
	375
	376	=over 2
	377
	378	=item -
	379
	380	Perl 5.8 or later
	381
	382	=item -
	383
	384	File::Basename
	385
	386	=item -
	387
	388	Getopt::Std
	389
	390	=item -
	391
	392	Net::DNS I<(CPAN)>
	393
	394	=item -
	395
	396	Net::SMTP
	397
	398	=back
	399
	400	Furthermore you'll need a working DNS installation.
	401
	402	=head1 DESCRIPTION
	403
	404	checkmail checks the vailidity / deliverability of a mail address.
	405	You may submit just one address as the last argument or a file
	406	containing one address on each line using the B<-f> option.
	407
	408	=head2 Configuration
	409
	410	For the time being, all configuration is done in the script. You have
	411	to set the following elements of the %config hash:
	412
	413	=over 4
	414
	415	=item B<$config{'helo'}>
	416
	417	The hostname to be used for I<HELO> or I<EHLO> in the SMTP dialog.
	418
	419	=item B<$config{'from'}>
	420
	421	The sender address to be used for I<MAIL FROM> while testing.
	422
	423	=item B<$config{'rand'}>
	424
	425	A "random" local part to construct a reliably invalid address for use
	426	with the B<-r> option.
	427
	428	=back
	429
	430	=head2 Usage
	431
	432	After configuring the script you may run your first test with
	433
	434	checkmail user@example.org
	435
	436	B<checkmail> will try to determine the mail exchanger(s) (MX)
	437	responsible for I<example.org> by querying the DNS for the respective
	438	MX records and then try to connect via SMTP (on port 25) to each of
	439	them in order of precedence (if necessary). It will run through the
	440	SMTP dialog until just before the I<DATA> stage, i.e. doing I<EHLO>,
	441	I<MAIL FROM> and I<RCPT TO>. If no MX is defined, B<checkmail> will
	442	fall back to the I<example.org> host itself, provided there is at
	443	least one A record defined in the DNS. If there are neither MX nor A
	444	records for I<example.org>, mail is not deliverable and B<checkmail>
	445	will fail accordingly. If no host can be reached, B<checkmail> will
	446	fail, too. Finally B<checkmail> will fail if mail to the given
	447	recipient is not accepted by the respective host.
	448
	449	If B<checkmail> fails, you'll not be able to deliver mail to that
	450	address - at least not using the configured sender address and from
	451	the host you're testing from. However, the opposite is not true: a
	452	mail you send may still not be delivered even if a test via
	453	B<checkmail> succeeds. The receiving entity may reject your mail after
	454	the I<DATA> stage, due to content checking or without any special
	455	reason, or it may even drop, filter or bounce your mail after finally
	456	accepting it. There is no way to be sure a mail will be accepted short
	457	of sending a real mail to the address in question.
	458
	459	You may, however, try to detect hosts that will happily accept any and
	460	all recipient in the SMTP dialog and just reject your mail later on,
	461	for example to defeat exactly the kind of check you try to do.
	462	B<checkmail> will do that by submitting a recipient address that is
	463	known to be invalid; if that address is accepted, too, you'll know
	464	that you can't reliably check the validity of any address on that
	465	host. You can force that check by using the B<-r> option.
	466
	467	If you don't want to see just the results of your test, you can get a
	468	B<complete log> of the SMTP dialog by using the B<-l> option. That may be
	469	helpful to test for temporary failure conditions.
	470
	471	On the other hand you may use the B<-q> option to suppress all output;
	472	B<checkmail> will then terminate with one of the following B<exit
	473	status>:
	474
	475	=over 4
	476
	477	=item B<0>
	478
	479	address(es) seem/seems to be valid
	480
	481	=item B<1>
	482
	483	temporary error (connection failure or temporary failure)
	484
	485	=item B<2>
	486
	487	address is invalid
	488
	489	=item B<3>
	490
	491	address cannot reliably be checked (test using B<-r> failed)
	492
	493	=back
	494
	495	You can do B<batch processing> using B<-f> and submitting a file with
	496	one address on each line. In that case the exit status is set to the
	497	highest value generated by testing all addresses, i.e. it is set to
	498	B<0> if and only if no adress failed, but to B<2> if even one address
	499	failed and to B<3> if even one addresses couldn't reliably be checked.
	500
	501	And finally you can B<suppress DNS lookups> for MX and A records and
	502	just force B<checkmail> to connect to a particular host using the
	503	B<-m> option.
	504
	505	B<Please note:> You shouldn't try to validate addresses while working
	506	from a dial-up or blacklisted host. If in doubt, use the B<-l> option
	507	to have a closer look on the SMTP dialog yourself.
	508
	509	=head1 OPTIONS
	510
	511	=over 3
	512
	513	=item B<-V> (version)
	514
	515	Print out version and copyright information on B<checkmail> and exit.
	516
	517	=item B<-h> (help)
	518
	519	Print this man page and exit.
	520
	521	=item B<-q> (quit)
	522
	523	Suppress output and just terminate with a specific exit status.
	524
	525	=item B<-l> (log)
	526
	527	Log and print out the whole SMTP dialog.
	528
	529	=item B<-r> (random address)
	530
	531	Also try a reliably invalid address - defined in B<$config{'rand'}> -
	532	to catch hosts that try undermine address verification.
	533
	534	=item B<-m> I<host> (MX to use)
	535
	536	Force a connection to I<host> to check deliverability to that
	537	particular host irrespective of DNS entries. For example:
	538
	539	checkmail -m test.host.example user@domain.example
	540
	541	=item B<-f> I<file> (file)
	542
	543	Process all addresses from I<file> (one on each line).
	544
	545	=back
	546
	547	=head1 INSTALLATION
	548
	549	Just copy checkmail to some directory and get started.
	550
	551	You can run your first test with
	552
	553	checkmail user@example.org
	554
	555	=head1 ENVIRONMENT
	556
	557	See documentation of I<Net::DNS::Resolver>.
	558
	559	=head1 FILES
	560
	561	=over 4
	562
	563	=item F<checkmail.pl>
	564
	565	The script itself.
	566
	567	=back
	568
	569	=head1 BUGS
	570
	571	Please report any bugs or feature request to the author or use the
	572	bug tracker at L<http://bugs.th-h.de/>!
	573
	574	=head1 SEE ALSO
	575
	576	L<http://th-h.de/download/scripts.php> will have the current
	577	version of this program.
	578
	579	This program is maintained using the Git version control system. You
	580	may clone L<git://code.th-h.de/mail/checkmail.git> to check out the
	581	current development tree or browse it on the web via
	582	L<http://code.th-h.de/?p=mail/checkmail.git>.
	583
	584	=head1 AUTHOR
	585
	586	Thomas Hochstein <thh@inter.net>
	587
	588	=head1 COPYRIGHT AND LICENSE
	589
	590	Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>
	591
	592	This program is free software; you may redistribute it and/or modify it
	593	under the same terms as Perl itself.
	594
	595	=cut