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(@message);
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 $status = connection_failed(@message);
215 # verification impossible?
218 print " > Address verificaton impossible. You'll have to send a test mail ...\n" if !($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 $$logr .= sprintf("No %s records found: %s\n",$type,parse_dns_reply($error));
296 ################################## try_rcpt_to #################################
297 # send RCPT TO and return replies
298 # IN : \$smtp : a reference to an SMTP object
299 # $recipient: a mail address
300 # \$log : reference to the log (to be printed out via -l)
301 # OUT: $success: exit code (0 for false, 1 for true, -1 for tempfail)
302 # $code : SMTP status code
303 # $message: SMTP status message
304 # \$log will be changed
306 my($smtpr,$recipient,$logr)=@_;
307 $$logr .= sprintf("RCPT TO:<%s>\n",$recipient);
309 $$smtpr->to($recipient);
311 log_smtp_reply($logr,$$smtpr->code,$$smtpr->message);
312 $success = analyze_smtp_reply($$smtpr->code,$$smtpr->message);
315 $$logr .= "---Connection failure---\n";
317 return ($success,$$smtpr->code,$$smtpr->message);
320 ################################ log_smtp_reply ################################
321 # log result of SMTP command
322 # IN : \$log : reference to the log (to be printed out via -l)
323 # $code : SMTP status code
324 # @message : SMTP status message
326 # \$log will be changed
328 my($logr,$code,@message)=@_;
329 $$logr .= sprintf('%s %s',$code,join('- ',@message));
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);
343 } elsif ($type == 5) {
345 } elsif ($type == 4) {
351 ############################## connection_failed ###############################
352 # print failure message and return status 1
353 # IN : @message : SMTP status message
355 sub connection_failed {
357 print " ! Connection failed or other temporary failure.\n" if !($options{'q'});
358 printf(" %s\n",join(' ',@message)) if @message;
364 ################################ Documentation #################################
368 checkmail - check deliverability of a mail address
372 B<checkmail> [B<-Vhqlr>] [B<-m> I<host>] I<address>|B<-f> I<file>
400 Furthermore you'll need a working DNS installation.
404 checkmail checks the vailidity / deliverability of a mail address.
405 You may submit just one address as the last argument or a file
406 containing one address on each line using the B<-f> option.
410 For the time being, all configuration is done in the script. You have
411 to set the following elements of the %config hash:
415 =item B<$config{'helo'}>
417 The hostname to be used for I<HELO> or I<EHLO> in the SMTP dialog.
419 =item B<$config{'from'}>
421 The sender address to be used for I<MAIL FROM> while testing.
423 =item B<$config{'rand'}>
425 A "random" local part to construct a reliably invalid address for use
426 with the B<-r> option.
432 After configuring the script you may run your first test with
434 checkmail user@example.org
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.
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.
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.
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.
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
479 address(es) seem/seems to be valid
483 temporary error (connection failure or temporary failure)
491 address cannot reliably be checked (test using B<-r> failed)
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.
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
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.
513 =item B<-V> (version)
515 Print out version and copyright information on B<checkmail> and exit.
519 Print this man page and exit.
523 Suppress output and just terminate with a specific exit status.
527 Log and print out the whole SMTP dialog.
529 =item B<-r> (random address)
531 Also try a reliably invalid address - defined in B<$config{'rand'}> -
532 to catch hosts that try undermine address verification.
534 =item B<-m> I<host> (MX to use)
536 Force a connection to I<host> to check deliverability to that
537 particular host irrespective of DNS entries. For example:
539 checkmail -m test.host.example user@domain.example
541 =item B<-f> I<file> (file)
543 Process all addresses from I<file> (one on each line).
549 Just copy checkmail to some directory and get started.
551 You can run your first test with
553 checkmail user@example.org
557 See documentation of I<Net::DNS::Resolver>.
563 =item F<checkmail.pl>
571 Please report any bugs or feature request to the author or use the
572 bug tracker at L<http://bugs.th-h.de/>!
576 L<http://th-h.de/download/scripts.php> will have the current
577 version of this program.
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>.
586 Thomas Hochstein <thh@inter.net>
588 =head1 COPYRIGHT AND LICENSE
590 Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>
592 This program is free software; you may redistribute it and/or modify it
593 under the same terms as Perl itself.