3 # checkmail Version 0.3 by Thomas Hochstein
5 # This script tries to verify the deliverability of (a) mail address(es).
7 # Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>
9 # It can be redistributed and/or modified under the same terms under
10 # which Perl itself is published.
14 ################################# Configuration ################################
15 # Please fill in a working configuration!
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
25 ################################### Modules ####################################
32 ################################# Main program #################################
34 $Getopt::Std::STANDARD_HELP_VERSION = 1;
35 my $myself = basename($0);
37 # read commandline options
39 getopts('Vhqlrf:m:', \%options);
43 print "$myself v $VERSION\nCopyright (c) 2010 Thomas Hochstein <thh\@inter.net>\n";
44 print "This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.\n";
48 # -h: feed myself to perldoc
54 # display usage information if neither -f nor an address are present
55 if (!$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";
68 # -f: open file and read addresses to @adresses
71 if (-e $options{'f'}) {
72 open FILE, "<$options{'f'}" or die("$myself ERROR: Could not open file $options{'f'} for reading: $!");
74 die("$myself ERROR: File $options{'f'} does not exist!\n");
81 # fill @adresses with single address to check
83 push(@addresses,$ARGV[0]);
86 # loop over each address and test it
87 my (%targets,$curstat,$status,$log,$message);
88 foreach (@addresses) {
90 (undef,my $domain) = splitaddress($address);
91 printf(" * Testing %s ...\n",$address) if !($options{'q'});
92 $log .= "\n===== BEGIN $address =====\n";
93 # get list of target hosts or take host forced via -m
95 %targets = %{gettargets($domain,\$log)};
97 $message = sprintf("Connection to %s forced by -m.\n",$options{'m'});
99 print " $message" if !($options{'q'});
100 # just one target host with preference 0
101 $targets{$options{'m'}} = 0;
104 $curstat = checkaddress($address,\%targets,\$log);
107 $message = 'DNS lookup failure';
108 printf(" > Address is INVALID (%s).\n",$message) if !($options{'q'});
109 $log .= $message . '.';
111 $log .= "====== END $address ======\n";
112 $status = $curstat if (!defined($status) or $curstat > $status);
115 print $log if ($options{'l'});
117 # status 0: valid / batch processing
118 # 1: connection failed or temporary failure
121 #D print "\n-> EXIT $status\n";
124 ################################## gettargets ##################################
125 # get mail exchanger(s) or A record(s) for a domain
126 # IN : $domain: domain to query the DNS for
127 # OUT: \%targets: reference to a hash containing a list of target hosts
129 my ($domain,$logr) = @_;
131 my $resolver = Net::DNS::Resolver->new(udp_timeout => 15, tcp_timeout => 15);
134 # get MX record(s) as a list sorted by preference
135 if (my @mxrr = mx($resolver,$domain)) {
136 print_dns_result($domain,'MX',scalar(@mxrr),undef,$logr);
137 foreach my $rr (@mxrr) {
138 $targets{$rr->exchange} = $rr->preference;
139 $$logr .= sprintf("(%d) %s\n",$rr->preference,$rr->exchange);
141 # no MX record found; log and try A record(s)
143 print_dns_result($domain,'MX',undef,$resolver->errorstring,$logr);
144 print(" Falling back to A record ...\n") if !($options{'q'});
146 if (my $query = $resolver->query($domain,'A','IN')) {
147 print_dns_result($domain,'A',$query->header->ancount,undef,$logr);
148 foreach my $rr ($query->answer) {
149 $targets{$rr->address} = 0;
150 $$logr .= sprintf("- %s\n",$rr->address);
152 # no A record found either; log and fail
154 print_dns_result($domain,'A',undef,$resolver->errorstring,$logr);
155 printf(" %s has neither MX nor A records - mail cannot be delivered.\n",$domain) if !($options{'q'});
161 ################################# checkaddress #################################
162 # test address for deliverability
163 # IN : $address: adress to be tested
164 # \%targets: reference to a hash containing a list of MX hosts
165 # \$log : reference to the log (to be printed out via -l)
167 # \$log will be changed
169 my ($address,$targetsr,$logr) = @_;
170 my %targets = %{$targetsr};
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 $$logr .= sprintf("%s:\n%s\n",$host,"-" x (length($host)+1));
176 $status = checksmtp($address,$host,$logr);
177 last if ($status != 1);
182 ################################### checksmtp ##################################
183 # connect to a remote machine on port 25 and test deliverability of a mail
184 # address by doing the SMTP dialog until RCPT TO stage
185 # IN : $address: address to test
186 # $target : target host
187 # \$log : reference to the log (to be printed out via -l)
188 # OUT: .........: reference to a hash containing a list of target hosts
189 # \$log will be changed
191 my ($address,$target,$logr) = @_;
193 # start SMTP connection
194 if (my $smtp = Net::SMTP->new($target,Hello => $config{'helo'},Timeout => 30)) {
195 $$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);
202 my ($success,$code,@message) = try_rcpt_to(\$smtp,$address,$logr);
203 # connection failure?
205 $status = connection_failed();
206 # delivery attempt was successful?
208 # -r: try random address (which should be guaranteed to be invalid)
210 (undef,my $domain) = splitaddress($address);
211 my ($success,$code,@message) = try_rcpt_to(\$smtp,$config{'rand'}.'@'.$domain,$logr);
212 # connection failure?
214 $status = connection_failed();
215 # verification impossible?
218 print " > Address verificaton impossible. You'll have to send a test mail ...\n" if !($options{'q'});
221 # if -r is not set or status was not set to 3: valid address
222 if (!defined($status)) {
224 print " > Address is valid.\n" if !($options{'q'});
226 # delivery attempt failed?
229 print " > Address is INVALID:\n" if !($options{'q'});
230 print ' ' . join(' ',@message) if !($options{'q'});
232 # terminate SMTP connection
235 log_smtp_reply($logr,$smtp->code,$smtp->message);
237 # SMTP connection failed / timeout
238 $status = connection_failed();
239 $$logr .= "---Connection failure---\n";
244 ################################# splitaddress #################################
245 # split mail address into local and domain part
246 # IN : $address: a mail address
247 # OUT: $local : local part
248 # $domain: domain part
251 (my $lp = $address) =~ s/^([^@]+)@.*/$1/;
252 (my $domain = $address) =~ s/[^@]+\@(\S*)$/$1/;
253 return ($lp,$domain);
256 ################################ parse_dns_reply ###############################
257 # parse DNS response codes and return code and description
258 # IN : $response: a DNS response code
259 # OUT: "$response ($desciption)"
260 sub parse_dns_reply {
262 my %dnsrespcodes = (NOERROR => 'empty response',
263 NXDOMAIN => 'non-existent domain',
264 SERVFAIL => 'DNS server failure',
265 REFUSED => 'DNS query refused',
266 FORMERR => 'format error',
267 NOTIMP => 'not implemented');
268 if(defined($dnsrespcodes{$response})) {
269 return sprintf('%s (%s)',$response,$dnsrespcodes{$response});
275 ############################### print_dns_result ###############################
276 # print and log result of DNS query
277 # IN : $domain: domain the DNS was queried for
278 # $type : record type (MX, A, ...)
279 # $count : number of records found
280 # $error : DNS response code
281 # \$log : reference to the log (to be printed out via -l)
283 # \$log will be changed
284 sub print_dns_result {
285 my ($domain,$type,$count,$error,$logr) = @_;
286 if (defined($count)) {
287 printf(" %d %s record(s) found for %s\n",$count,$type,$domain) if !($options{'q'});
288 $$logr .= sprintf("%s DNS record(s):\n",$type);
290 printf(" No %s records found for %s: %s\n",$type,$domain,parse_dns_reply($error)) if !($options{'q'});
291 $$logr .= sprintf("No %s records found: %s\n",$type,parse_dns_reply($error));
296 ################################## try_rcpt_to #################################
297 # send RCPT TO and return replies
298 # IN : \$smtp : a reference to an SMTP object
299 # $recipient: a mail address
300 # \$log : reference to the log (to be printed out via -l)
301 # OUT: $success: true or false
302 # $code : SMTP status code
303 # $message: SMTP status message
304 # \$log will be changed
306 my($smtpr,$recipient,$logr)=@_;
307 $$logr .= sprintf("RCPT TO:<%s>\n",$recipient);
308 my $success = $$smtpr->to($recipient);
310 log_smtp_reply($logr,$$smtpr->code,$$smtpr->message);
313 $$logr .= "---Connection failure---\n";
315 return ($success,$$smtpr->code,$$smtpr->message);
318 ################################ log_smtp_reply ################################
319 # log result of SMTP command
320 # IN : \$log : reference to the log (to be printed out via -l)
321 # $code : SMTP status code
322 # @message : SMTP status message
324 # \$log will be changed
326 my($logr,$code,@message)=@_;
327 $$logr .= sprintf('%s %s',$code,join('- ',@message));
331 ############################## connection_failed ###############################
332 # print failure message and return status 1
334 sub connection_failed {
335 print " > Connection failure.\n" if !($options{'q'});
341 ################################ Documentation #################################
345 checkmail - check deliverability of a mail address
349 B<checkmail> [B<-Vhqlr>] [B<-m> I<host>] I<address>|B<-f> I<file>
377 Furthermore you'll need a working DNS installation.
381 checkmail checks the vailidity / deliverability of a mail address.
382 You may submit just one address as the last argument or a file
383 containing one address on each line using the B<-f> option.
387 For the time being, all configuration is done in the script. You have
388 to set the following elements of the %config hash:
392 =item B<$config{'helo'}>
394 The hostname to be used for I<HELO> or I<EHLO> in the SMTP dialog.
396 =item B<$config{'from'}>
398 The sender address to be used for I<MAIL FROM> while testing.
400 =item B<$config{'rand'}>
402 A "random" local part to construct a reliably invalid address for use
403 with the B<-r> option.
409 After configuring the script you may run your first test with
411 checkmail user@example.org
413 B<checkmail> will try to determine the mail exchanger(s) (MX)
414 responsible for I<example.org> by querying the DNS for the respective
415 MX records and then try to connect via SMTP (on port 25) to each of
416 them in order of precedence (if necessary). It will run through the
417 SMTP dialog until just before the I<DATA> stage, i.e. doing I<EHLO>,
418 I<MAIL FROM> and I<RCPT TO>. If no MX is defined, B<checkmail> will
419 fall back to the I<example.org> host itself, provided there is at
420 least one A record defined in the DNS. If there are neither MX nor A
421 records for I<example.org>, mail is not deliverable and B<checkmail>
422 will fail accordingly. If no host can be reached, B<checkmail> will
423 fail, too. Finally B<checkmail> will fail if mail to the given
424 recipient is not accepted by the respective host.
426 If B<checkmail> fails, you'll not be able to deliver mail to that
427 address - at least not using the configured sender address and from
428 the host you're testing from. However, the opposite is not true: a
429 mail you send may still not be delivered even if a test via
430 B<checkmail> succeeds. The receiving entity may reject your mail after
431 the I<DATA> stage, due to content checking or without any special
432 reason, or it may even drop, filter or bounce your mail after finally
433 accepting it. There is no way to be sure a mail will be accepted short
434 of sending a real mail to the address in question.
436 You may, however, try to detect hosts that will happily accept any and
437 all recipient in the SMTP dialog and just reject your mail later on,
438 for example to defeat exactly the kind of check you try to do.
439 B<checkmail> will do that by submitting a recipient address that is
440 known to be invalid; if that address is accepted, too, you'll know
441 that you can't reliably check the validity of any address on that
442 host. You can force that check by using the B<-r> option.
444 If you don't want to see just the results of your test, you can get a
445 B<complete log> of the SMTP dialog by using the B<-l> option. That may be
446 helpful to test for temporary failure conditions.
448 On the other hand you may use the B<-q> option to suppress all output;
449 B<checkmail> will then terminate with one of the following B<exit
456 address(es) seem/seems to be valid
460 temporary error (connection failure or temporary failure)
468 address cannot reliably be checked (test using B<-r> failed)
472 You can do B<batch processing> using B<-f> and submitting a file with
473 one address on each line. In that case the exit status is set to the
474 highest value generated by testing all addresses, i.e. it is set to
475 B<0> if and only if no adress failed, but to B<2> if even one address
476 failed and to B<3> if even one addresses couldn't reliably be checked.
478 And finally you can B<suppress DNS lookups> for MX and A records and
479 just force B<checkmail> to connect to a particular host using the
482 B<Please note:> You shouldn't try to validate addresses while working
483 from a dial-up or blacklisted host. If in doubt, use the B<-l> option
484 to have a closer look on the SMTP dialog yourself.
490 =item B<-V> (version)
492 Print out version and copyright information on B<checkmail> and exit.
496 Print this man page and exit.
500 Suppress output and just terminate with a specific exit status.
504 Log and print out the whole SMTP dialog.
506 =item B<-r> (random address)
508 Also try a reliably invalid address - defined in B<$config{'rand'}> -
509 to catch hosts that try undermine address verification.
511 =item B<-m> I<host> (MX to use)
513 Force a connection to I<host> to check deliverability to that
514 particular host irrespective of DNS entries. For example:
516 checkmail -m test.host.example user@domain.example
518 =item B<-f> I<file> (file)
520 Process all addresses from I<file> (one on each line).
526 Just copy checkmail to some directory and get started.
528 You can run your first test with
530 checkmail user@example.org
534 See documentation of I<Net::DNS::Resolver>.
540 =item F<checkmail.pl>
548 Please report any bugs or feature request to the author or use the
549 bug tracker at L<http://bugs.th-h.de/>!
553 L<http://th-h.de/download/scripts.php> will have the current
554 version of this program.
556 This program is maintained using the Git version control system. You
557 may clone L<git://code.th-h.de/mail/checkmail.git> to check out the
558 current development tree or browse it on the web via
559 L<http://code.th-h.de/?p=mail/checkmail.git>.
563 Thomas Hochstein <thh@inter.net>
565 =head1 COPYRIGHT AND LICENSE
567 Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>
569 This program is free software; you may redistribute it and/or modify it
570 under the same terms as Perl itself.