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1#! /usr/bin/perl -w
2#
3# checkmail Version 0.6.3 by Thomas Hochstein
4#
5# This script tries to verify the deliverability of (a) mail address(es).
6#
7# Copyright (c) 2002-2016 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
12our $VERSION = "0.6.3 (unreleased)";
13
14################################# Configuration ################################
15# Please fill in a working configuration!
16my %config=(
17 # value used for HELO/EHLO - a valid hostname you own
18 helo => 'testhost.domain.example',
19 # value used for MAIL FROM: - a valid address under your control
20 from => 'mailtest@testhost.domain.example'
21 );
22
23################################### Modules ####################################
24use strict;
25use File::Basename;
26use Getopt::Std;
27use Mail::Address;
28use Net::DNS;
29use Net::SMTP;
30
31################################# Main program #################################
32
33$Getopt::Std::STANDARD_HELP_VERSION = 1;
34my $myself = basename($0);
35
36# read commandline options
37my %options;
38getopts('Vhqlrf:m:s:e:', \%options);
39
40# -V: display version
41if ($options{'V'}) {
42 print "$myself v $VERSION\nCopyright (c) 2002-2016 Thomas Hochstein <thh\@inter.net>\n";
43 print "This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.\n";
44 exit(100);
45};
46
47# -h: feed myself to perldoc
48if ($options{'h'}) {
49 exec('perldoc', $0);
50 exit(100);
51};
52
53# display usage information if neither -f nor an address are present
54if (!$options{'f'} and !$ARGV[0]) {
55 print "Usage: $myself [-hqlr] [-m <host>] [-s <from>] [-e <EHLO>] <address>|-f <file>\n";
56 print "Options: -V display copyright and version\n";
57 print " -h show documentation\n";
58 print " -q quiet (no output, just exit with 0/1/2/3)\n";
59 print " -l extended logging\n";
60 print " -r test random address to verify verification\n";
61 print " -m <host> no DNS lookup, just test this host\n";
62 print " -s <from> override configured value for MAIL FROM\n";
63 print " -e <EHLO> override configured value for EHLO\n";
64 print " <address> mail address to check\n\n";
65 print " -f <file> parse file (one address per line)\n";
66 exit(100);
67};
68
69# -s / -e: override configuration
70$config{'from'} = $options{'s'} if defined($options{'s'});
71$config{'helo'} = $options{'e'} if $options{'e'};
72
73# -f: open file and read addresses to @adresses
74my @addresses;
75if ($options{'f'}) {
76 if (-e $options{'f'}) {
77 open FILE, "<$options{'f'}" or die("$myself ERROR: Could not open file $options{'f'} for reading: $!");
78 } else {
79 die("$myself ERROR: File $options{'f'} does not exist!\n");
80 };
81 while(<FILE>) {
82 chomp;
83 push(@addresses,$_);
84 };
85 close FILE;
86# fill @adresses with single address to check
87 } else {
88 push(@addresses,$ARGV[0]);
89};
90
91# loop over each address and test it
92my (%targets,$curstat,$status,$log,$message);
93foreach (@addresses) {
94 my $address = $_;
95 # regexp taken from http://www.regular-expressions.info/email.html
96 # with escaping of "/" added two times and "*" changed to "+"
97 # in localpart, second alternative
98 if ($address !~ /^(?:[a-z0-9!#$%&'*+\/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+\/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f]+)")@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?$/i) {
99 printf(" > Address <%s> is syntactically INVALID.\n",$address) if !($options{'q'});
100 $curstat = 2;
101 } else {
102 my $domain = Mail::Address->new('',$address)->host;
103 printf(" * Testing %s ...\n",$address) if !($options{'q'});
104 $log .= "\n===== BEGIN $address =====\n";
105 # get list of target hosts or take host forced via -m
106 if (!$options{'m'}) {
107 %targets = %{gettargets($domain,\$log)};
108 } else {
109 $message = sprintf("Connection to %s forced by -m.\n",$options{'m'});
110 $log .= $message;
111 print " $message" if !($options{'q'});
112 # just one target host with preference 0
113 $targets{$options{'m'}} = 0;
114 };
115 if (%targets) {
116 $curstat = checkaddress($address,\%targets,\$log);
117 } else {
118 $curstat = 2;
119 $message = 'DNS lookup failure';
120 printf(" > Address is INVALID (%s).\n",$message) if !($options{'q'});
121 $log .= $message . '.';
122 };
123 $log .= "====== END $address ======\n";
124 };
125 $status = $curstat if (!defined($status) or $curstat > $status);
126};
127
128print $log if ($options{'l'});
129
130# status 0: valid / batch processing
131# 1: connection failed or temporary failure
132# 2: invalid
133# 3: cannot verify
134#D print "\n-> EXIT $status\n";
135exit($status);
136
137################################## gettargets ##################################
138# get mail exchanger(s) or A record(s) for a domain
139# IN : $domain: domain to query the DNS for
140# OUT: \%targets: reference to a hash containing a list of target hosts
141sub gettargets {
142 my ($domain,$logr) = @_;
143 # resolver objekt
144 my $resolver = Net::DNS::Resolver->new(udp_timeout => 15, tcp_timeout => 15);
145
146 my %targets;
147 # get MX record(s) as a list sorted by preference
148 if (my @mxrr = mx($resolver,$domain)) {
149 print_dns_result($domain,'MX',scalar(@mxrr),undef,$logr);
150 foreach my $rr (@mxrr) {
151 $targets{$rr->exchange} = $rr->preference;
152 $$logr .= sprintf("(%d) %s\n",$rr->preference,$rr->exchange);
153 };
154 # no MX record found; log and try A record(s)
155 } else {
156 print_dns_result($domain,'MX',undef,$resolver->errorstring,$logr);
157 print(" Falling back to A record(s) ...\n") if !($options{'q'});
158 # get A record(s)
159 # may get CNAMEs instead ...
160 if (my $query = $resolver->query($domain,'A','IN')) {
161 print_dns_result($domain,'A/CNAME',$query->header->ancount,undef,$logr);
162 foreach my $rr ($query->answer) {
163 if ($rr->type ne 'A') {
164 # report CNAMEs and don't add them to target list
165 if ($rr->type eq 'CNAME') {
166 printf (" ~ '%s' is a CNAME for '%s' and will be resolved accordingly. \n",$rr->name,$rr->cname) if !($options{'q'});
167 $$logr .= sprintf("- CNAME resolved: %s -> %s\n",$rr->name,$rr->cname);
168 }
169 next;
170 }
171 $targets{$rr->address} = 0;
172 $$logr .= sprintf("- %s\n",$rr->address);
173 };
174 # no A record found either; log and fail
175 } else {
176 print_dns_result($domain,'A',undef,$resolver->errorstring,$logr);
177 printf(" %s has neither MX nor A records - mail cannot be delivered.\n",$domain) if !($options{'q'});
178 };
179 };
180 return \%targets;
181};
182
183################################# checkaddress #################################
184# test address for deliverability
185# IN : $address: adress to be tested
186# \%targets: reference to a hash containing a list of MX hosts
187# \$log : reference to the log (to be printed out via -l)
188# OUT: ---
189# \$log will be changed
190sub checkaddress {
191 my ($address,$targetsr,$logr) = @_;
192 my %targets = %{$targetsr};
193 my $status;
194 # walk %targets in order of preference
195 foreach my $host (sort { $targets{$a} <=> $targets{$b} } keys %targets) {
196 printf(" / Trying %s (%s) with %s\n",$host,$targets{$host} || 'A',$address) if !($options{'q'});
197 $$logr .= sprintf("%s:\n%s\n",$host,"-" x (length($host)+1));
198 $status = checksmtp($address,$host,$logr);
199 last if ($status != 1);
200 };
201 return $status;
202};
203
204################################### checksmtp ##################################
205# connect to a remote machine on port 25 and test deliverability of a mail
206# address by doing the SMTP dialog until RCPT TO stage
207# IN : $address: address to test
208# $target : target host
209# \$log : reference to the log (to be printed out via -l)
210# OUT: .........: reference to a hash containing a list of target hosts
211# \$log will be changed
212sub checksmtp {
213 my ($address,$target,$logr) = @_;
214 my ($status);
215 # start SMTP connection
216 if (my $smtp = Net::SMTP->new($target,Hello => $config{'helo'},Timeout => 30)) {
217 $$logr .= $smtp->banner; # Net::SMTP doesn't seem to support multiline greetings.
218 $$logr .= "EHLO $config{'helo'}\n";
219 log_smtp_reply($logr,$smtp->code,$smtp->message);
220 $smtp->mail($config{'from'});
221 $$logr .= "MAIL FROM:<$config{'from'}>\n";
222 log_smtp_reply($logr,$smtp->code,$smtp->message);
223 # test address
224 my ($success,$code,@message) = try_rcpt_to(\$smtp,$address,$logr);
225 # connection failure?
226 if ($success < 0) {
227 $status = connection_failed(@message);
228 # delivery attempt was successful?
229 } elsif ($success) {
230 # -r: try random address (which should be guaranteed to be invalid)
231 if ($options{'r'}) {
232 my ($success,$code,@message) = try_rcpt_to(\$smtp,create_rand_addr(Mail::Address->new('',$address)->host),$logr);
233 # connection failure?
234 if ($success < 0) {
235 $status = connection_failed(@message);
236 # reset status - the address has been checked and _is_ valid!
237 $status = 3;
238 print " > Address verification currently impossible. You'll have to try again or send a test mail ...\n" if !($options{'q'});
239 # verification impossible?
240 } elsif ($success) {
241 $status = 3;
242 print " > Address verification impossible. You'll have to send a test mail ...\n" if !($options{'q'});
243 }
244 }
245 # if -r is not set or status was not set to 3: valid address
246 if (!defined($status)) {
247 $status = 0;
248 print " > Address is valid.\n" if !($options{'q'});
249 };
250 # delivery attempt failed?
251 } else {
252 $status = 2;
253 print " > Address is INVALID:\n" if !($options{'q'});
254 print ' ' . join(' ',@message) if !($options{'q'});
255 }
256 # terminate SMTP connection
257 $smtp->quit;
258 $$logr .= "QUIT\n";
259 log_smtp_reply($logr,$smtp->code,$smtp->message);
260 } else {
261 # SMTP connection failed / timeout
262 $status = connection_failed();
263 $$logr .= "---Connection failure---\n";
264 };
265 return $status;
266}
267
268############################### create_rand_addr ###############################
269# create a random mail address
270# IN : $domain: the domain part
271# OUT: $address: the address
272sub create_rand_addr {
273 my($domain)=@_;
274 my $allowed = 'ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjkmnpqrstuvwxyz23456789-+_=';
275 my $address = '';
276 while (length($address) < 15) {
277 $address .= substr($allowed, (int(rand(length($allowed)))),1);
278 };
279 return ($address.'@'.$domain);
280};
281
282################################ parse_dns_reply ###############################
283# parse DNS response codes and return code and description
284# IN : $response: a DNS response code
285# OUT: "$response ($desciption)"
286sub parse_dns_reply {
287 my($response)=@_;
288 my %dnsrespcodes = (NOERROR => 'empty response',
289 NXDOMAIN => 'non-existent domain',
290 SERVFAIL => 'DNS server failure',
291 REFUSED => 'DNS query refused',
292 FORMERR => 'format error',
293 NOTIMP => 'not implemented');
294 if(defined($dnsrespcodes{$response})) {
295 return sprintf('%s (%s)',$response,$dnsrespcodes{$response});
296 } else {
297 return $response;
298 };
299};
300
301############################### print_dns_result ###############################
302# print and log result of DNS query
303# IN : $domain: domain the DNS was queried for
304# $type : record type (MX, A, ...)
305# $count : number of records found
306# $error : DNS response code
307# \$log : reference to the log (to be printed out via -l)
308# OUT: ---
309# \$log will be changed
310sub print_dns_result {
311 my ($domain,$type,$count,$error,$logr) = @_;
312 if (defined($count)) {
313 printf(" %d %s record(s) found for %s\n",$count,$type,$domain) if !($options{'q'});
314 $$logr .= sprintf("%s DNS record(s):\n",$type);
315 } else {
316 printf(" No %s records found for %s: %s\n",$type,$domain,parse_dns_reply($error)) if !($options{'q'});
317 $$logr .= sprintf("No %s records found: %s\n",$type,parse_dns_reply($error));
318 };
319 return;
320};
321
322################################## try_rcpt_to #################################
323# send RCPT TO and return replies
324# IN : \$smtp : a reference to an SMTP object
325# $recipient: a mail address
326# \$log : reference to the log (to be printed out via -l)
327# OUT: $success: exit code (0 for false, 1 for true, -1 for tempfail)
328# $code : SMTP status code
329# $message: SMTP status message
330# \$log will be changed
331sub try_rcpt_to {
332 my($smtpr,$recipient,$logr)=@_;
333 $$logr .= sprintf("RCPT TO:<%s>\n",$recipient);
334 my $success;
335 $$smtpr->to($recipient);
336 if ($$smtpr->code) {
337 log_smtp_reply($logr,$$smtpr->code,$$smtpr->message);
338 $success = analyze_smtp_reply($$smtpr->code,$$smtpr->message);
339 } else {
340 $success = -1;
341 $$logr .= "---Connection failure---\n";
342 };
343 return ($success,$$smtpr->code,$$smtpr->message);
344};
345
346################################ log_smtp_reply ################################
347# log result of SMTP command
348# IN : \$log : reference to the log (to be printed out via -l)
349# $code : SMTP status code
350# @message : SMTP status message
351# OUT: ---
352# \$log will be changed
353sub log_smtp_reply {
354 my($logr,$code,@message)=@_;
355 $$logr .= sprintf('%s %s',$code,join('- ',@message));
356 return;
357}
358
359############################### analyze_smtp_reply ##############################
360# analyze SMTP response codes and messages
361# IN : $code : SMTP status code
362# @message : SMTP status message
363# OUT: exit code (0 for false, 1 for true, -1 for tempfail)
364sub analyze_smtp_reply {
365 my($code,@message)=@_;
366 my $type = substr($code, 0, 1);
367 if ($type == 2) {
368 return 1;
369 } elsif ($type == 5) {
370 return 0;
371 } elsif ($type == 4) {
372 return -1;
373 };
374 return -1;
375}
376
377############################## connection_failed ###############################
378# print failure message and return status 1
379# IN : @message : SMTP status message
380# OUT: 1
381sub connection_failed {
382 my(@message)=@_;
383 print " ! Connection failed or other temporary failure.\n" if !($options{'q'});
384 printf(" %s\n",join(' ',@message)) if @message;
385 return 1;
386}
387
388__END__
389
390################################ Documentation #################################
391
392=head1 NAME
393
394checkmail - check deliverability of a mail address
395
396=head1 SYNOPSIS
397
398B<checkmail> [B<-Vhqlr>] [B<-m> I<host>] [-s I<sender>] [-e I<EHLO>] I<address>|B<-f> I<file>
399
400=head1 REQUIREMENTS
401
402=over 2
403
404=item -
405
406Perl 5.8 or later
407
408=item -
409
410File::Basename
411
412=item -
413
414Getopt::Std
415
416=item -
417
418Mail::Address I<(CPAN)>
419
420=item -
421
422Net::DNS I<(CPAN)>
423
424=item -
425
426Net::SMTP
427
428=back
429
430Furthermore you'll need a working DNS installation.
431
432=head1 DESCRIPTION
433
434checkmail checks the vailidity / deliverability of a mail address.
435You may submit just one address as the last argument or a file
436containing one address on each line using the B<-f> option.
437
438=head2 Configuration
439
440For the time being, all configuration is done in the script. You have
441to set the following elements of the %config hash:
442
443=over 4
444
445=item B<$config{'helo'}>
446
447The hostname to be used for I<HELO> or I<EHLO> in the SMTP dialog.
448
449=item B<$config{'from'}>
450
451The sender address to be used for I<MAIL FROM> while testing.
452May be empty ('') to set '<>' as MAIL FROM.
453
454=back
455
456You may override that configuration by using the B<-e> and B<-s>
457command line options.
458
459=head2 Usage
460
461After configuring the script you may run your first test with
462
463 checkmail user@example.org
464
465B<checkmail> will check the address for syntactic validity. If the
466address is valid, it will try to determine the mail exchanger(s) (MX)
467responsible for I<example.org> by querying the DNS for the respective
468MX records and then try to connect via SMTP (on port 25) to each of
469them in order of precedence (if necessary). It will run through the
470SMTP dialog until just before the I<DATA> stage, i.e. doing I<EHLO>,
471I<MAIL FROM> and I<RCPT TO>. If no MX is defined, B<checkmail> will
472fall back to the I<example.org> host itself, provided there is at
473least one A record defined in the DNS. CNAMEs will be accepted and
474resolved here. If there are neither MX nor A records for
475I<example.org>, mail is not deliverable and B<checkmail> will fail
476accordingly. If no host can be reached, B<checkmail> will fail,
477too. Finally B<checkmail> will fail if mail to the given recipient
478is not accepted by the respective host.
479
480If B<checkmail> fails, you'll not be able to deliver mail to that
481address - at least not using the configured sender address and from
482the host you're testing from. However, the opposite is not true: a
483mail you send may still not be delivered even if a test via
484B<checkmail> succeeds. The receiving entity may reject your mail after
485the I<DATA> stage, due to content checking or without any special
486reason, or it may even drop, filter or bounce your mail after finally
487accepting it. There is no way to be sure a mail will be accepted short
488of sending a real mail to the address in question.
489
490You may, however, try to detect hosts that will happily accept any and
491all recipient in the SMTP dialog and just reject your mail later on,
492for example to defeat exactly the kind of check you try to do.
493B<checkmail> will do that by submitting a recipient address that is
494known to be invalid; if that address is accepted, too, you'll know
495that you can't reliably check the validity of any address on that
496host. You can force that check by using the B<-r> option.
497
498If you don't want to see just the results of your test, you can get a
499B<complete log> of the SMTP dialog by using the B<-l> option. That may be
500helpful to test for temporary failure conditions.
501
502On the other hand you may use the B<-q> option to suppress all output;
503B<checkmail> will then terminate with one of the following B<exit
504status>:
505
506=over 4
507
508=item B<0>
509
510address(es) seem/seems to be valid
511
512=item B<1>
513
514temporary error (connection failure or temporary failure)
515
516=item B<2>
517
518address is invalid
519
520=item B<3>
521
522address cannot reliably be checked (test using B<-r> failed)
523
524=back
525
526You can do B<batch processing> using B<-f> and submitting a file with
527one address on each line. In that case the exit status is set to the
528highest value generated by testing all addresses, i.e. it is set to
529B<0> if and only if no adress failed, but to B<2> if even one address
530failed and to B<3> if even one addresses couldn't reliably be checked.
531
532And finally you can B<suppress DNS lookups> for MX and A records and
533just force B<checkmail> to connect to a particular host using the
534B<-m> option.
535
536B<Please note:> You shouldn't try to validate addresses while working
537from a dial-up or blacklisted host. If in doubt, use the B<-l> option
538to have a closer look on the SMTP dialog yourself.
539
540B<Please note:> To avoid shell expansion on addresses you submit to
541B<checkmail>, use B<batch processing>.
542
543=head1 OPTIONS
544
545=over 3
546
547=item B<-V> (version)
548
549Print out version and copyright information on B<checkmail> and exit.
550
551=item B<-h> (help)
552
553Print this man page and exit.
554
555=item B<-q> (quit)
556
557Suppress output and just terminate with a specific exit status.
558
559=item B<-l> (log)
560
561Log and print out the whole SMTP dialog.
562
563=item B<-r> (random address)
564
565Also try a reliably invalid address to catch hosts that try undermine
566address verification.
567
568=item B<-m> I<host> (MX to use)
569
570Force a connection to I<host> to check deliverability to that
571particular host irrespective of DNS entries. For example:
572
573 checkmail -m test.host.example user@domain.example
574
575=item B<-s> I<sender> (value for MAIL FROM)
576
577Override configuration and use I<sender> for MAIL FROM.
578
579=item B<-e> I<EHLO> (value for EHLO)
580
581Override configuration and use I<EHLO> for EHLO.
582
583=item B<-f> I<file> (file)
584
585Process all addresses from I<file> (one on each line).
586
587=back
588
589=head1 INSTALLATION
590
591Just copy checkmail to some directory and get started.
592
593You can run your first test with
594
595 checkmail user@example.org
596
597=head1 ENVIRONMENT
598
599See documentation of I<Net::DNS::Resolver>.
600
601=head1 FILES
602
603=over 4
604
605=item F<checkmail.pl>
606
607The script itself.
608
609=back
610
611=head1 BUGS
612
613Please report any bugs or feature request to the author or use the
614bug tracker at L<http://bugs.th-h.de/>!
615
616=head1 SEE ALSO
617
618L<http://th-h.de/download/scripts.php> will have the current
619version of this program.
620
621This program is maintained using the Git version control system. You
622may clone L<git://code.th-h.de/mail/checkmail.git> to check out the
623current development tree or browse it on the web via
624L<http://code.th-h.de/?p=mail/checkmail.git>.
625
626=head1 AUTHOR
627
628Thomas Hochstein <thh@inter.net>
629
630=head1 COPYRIGHT AND LICENSE
631
632Copyright (c) 2002-2016 Thomas Hochstein <thh@inter.net>
633
634This program is free software; you may redistribute it and/or modify it
635under the same terms as Perl itself.
636
637=cut
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