3 # checkmail Version 0.6.3 by Thomas Hochstein
5 # This script tries to verify the deliverability of (a) mail address(es).
7 # Copyright (c) 2002-2016 Thomas Hochstein <thh@inter.net>
9 # It can be redistributed and/or modified under the same terms under
10 # which Perl itself is published.
12 our $VERSION = "0.6.3 (unreleased)";
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'
23 ################################### Modules ####################################
31 ################################# Main program #################################
33 $Getopt::Std::STANDARD_HELP_VERSION = 1;
34 my $myself = basename($0);
36 # read commandline options
38 getopts('Vhqlrf:m:s:e:', \%options);
42 print "$myself v $VERSION\nCopyright (c) 2010-2016 Thomas Hochstein <thh\@inter.net>\n";
43 print "This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.\n";
47 # -h: feed myself to perldoc
53 # display usage information if neither -f nor an address are present
54 if (!$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";
69 # -s / -e: override configuration
70 $config{'from'} = $options{'s'} if defined($options{'s'});
71 $config{'helo'} = $options{'e'} if $options{'e'};
73 # -f: open file and read addresses to @adresses
76 if (-e $options{'f'}) {
77 open FILE, "<$options{'f'}" or die("$myself ERROR: Could not open file $options{'f'} for reading: $!");
79 die("$myself ERROR: File $options{'f'} does not exist!\n");
86 # fill @adresses with single address to check
88 push(@addresses,$ARGV[0]);
91 # loop over each address and test it
92 my (%targets,$curstat,$status,$log,$message);
93 foreach (@addresses) {
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'});
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)};
109 $message = sprintf("Connection to %s forced by -m.\n",$options{'m'});
111 print " $message" if !($options{'q'});
112 # just one target host with preference 0
113 $targets{$options{'m'}} = 0;
116 $curstat = checkaddress($address,\%targets,\$log);
119 $message = 'DNS lookup failure';
120 printf(" > Address is INVALID (%s).\n",$message) if !($options{'q'});
121 $log .= $message . '.';
123 $log .= "====== END $address ======\n";
125 $status = $curstat if (!defined($status) or $curstat > $status);
128 print $log if ($options{'l'});
130 # status 0: valid / batch processing
131 # 1: connection failed or temporary failure
134 #D print "\n-> EXIT $status\n";
137 ################################## gettargets ##################################
138 # get mail exchanger(s) or A record(s) for a domain
139 # IN : $domain: domain to query the DNS for
140 # OUT: \%targets: reference to a hash containing a list of target hosts
142 my ($domain,$logr) = @_;
144 my $resolver = Net::DNS::Resolver->new(udp_timeout => 15, tcp_timeout => 15);
147 # get MX record(s) as a list sorted by preference
148 if (my @mxrr = mx($resolver,$domain)) {
149 print_dns_result($domain,'MX',scalar(@mxrr),undef,$logr);
150 foreach my $rr (@mxrr) {
151 $targets{$rr->exchange} = $rr->preference;
152 $$logr .= sprintf("(%d) %s\n",$rr->preference,$rr->exchange);
154 # no MX record found; log and try A record(s)
156 print_dns_result($domain,'MX',undef,$resolver->errorstring,$logr);
157 print(" Falling back to A record(s) ...\n") if !($options{'q'});
159 # may get CNAMEs instead ...
160 if (my $query = $resolver->query($domain,'A','IN')) {
161 print_dns_result($domain,'A/CNAME',$query->header->ancount,undef,$logr);
162 foreach my $rr ($query->answer) {
163 if ($rr->type ne 'A') {
164 # report CNAMEs and don't add them to target list
165 if ($rr->type eq 'CNAME') {
166 printf (" ~ '%s' is a CNAME for '%s' and will be resolved accordingly. \n",$rr->name,$rr->cname) if !($options{'q'});
167 $$logr .= sprintf("- CNAME resolved: %s -> %s\n",$rr->name,$rr->cname);
171 $targets{$rr->address} = 0;
172 $$logr .= sprintf("- %s\n",$rr->address);
174 # no A record found either; log and fail
176 print_dns_result($domain,'A',undef,$resolver->errorstring,$logr);
177 printf(" %s has neither MX nor A records - mail cannot be delivered.\n",$domain) if !($options{'q'});
183 ################################# checkaddress #################################
184 # test address for deliverability
185 # IN : $address: adress to be tested
186 # \%targets: reference to a hash containing a list of MX hosts
187 # \$log : reference to the log (to be printed out via -l)
189 # \$log will be changed
191 my ($address,$targetsr,$logr) = @_;
192 my %targets = %{$targetsr};
194 # walk %targets in order of preference
195 foreach my $host (sort { $targets{$a} <=> $targets{$b} } keys %targets) {
196 printf(" / Trying %s (%s) with %s\n",$host,$targets{$host} || 'A',$address) if !($options{'q'});
197 $$logr .= sprintf("%s:\n%s\n",$host,"-" x (length($host)+1));
198 $status = checksmtp($address,$host,$logr);
199 last if ($status != 1);
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 # $target : target host
209 # \$log : reference to the log (to be printed out via -l)
210 # OUT: .........: reference to a hash containing a list of target hosts
211 # \$log will be changed
213 my ($address,$target,$logr) = @_;
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 $$logr .= "MAIL FROM:<$config{'from'}>\n";
222 log_smtp_reply($logr,$smtp->code,$smtp->message);
224 my ($success,$code,@message) = try_rcpt_to(\$smtp,$address,$logr);
225 # connection failure?
227 $status = connection_failed(@message);
228 # delivery attempt was successful?
230 # -r: try random address (which should be guaranteed to be invalid)
232 my ($success,$code,@message) = try_rcpt_to(\$smtp,create_rand_addr(Mail::Address->new('',$address)->host),$logr);
233 # connection failure?
235 $status = connection_failed(@message);
236 # reset status - the address has been checked and _is_ valid!
238 print " > Address verification currently impossible. You'll have to try again or send a test mail ...\n" if !($options{'q'});
239 # verification impossible?
242 print " > Address verification impossible. You'll have to send a test mail ...\n" if !($options{'q'});
245 # if -r is not set or status was not set to 3: valid address
246 if (!defined($status)) {
248 print " > Address is valid.\n" if !($options{'q'});
250 # delivery attempt failed?
253 print " > Address is INVALID:\n" if !($options{'q'});
254 print ' ' . join(' ',@message) if !($options{'q'});
256 # terminate SMTP connection
259 log_smtp_reply($logr,$smtp->code,$smtp->message);
261 # SMTP connection failed / timeout
262 $status = connection_failed();
263 $$logr .= "---Connection failure---\n";
268 ############################### create_rand_addr ###############################
269 # create a random mail address
270 # IN : $domain: the domain part
271 # OUT: $address: the address
272 sub create_rand_addr {
274 my $allowed = 'ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjkmnpqrstuvwxyz23456789-+_=';
276 while (length($address) < 15) {
277 $address .= substr($allowed, (int(rand(length($allowed)))),1);
279 return ($address.'@'.$domain);
282 ################################ parse_dns_reply ###############################
283 # parse DNS response codes and return code and description
284 # IN : $response: a DNS response code
285 # OUT: "$response ($desciption)"
286 sub parse_dns_reply {
288 my %dnsrespcodes = (NOERROR => 'empty response',
289 NXDOMAIN => 'non-existent domain',
290 SERVFAIL => 'DNS server failure',
291 REFUSED => 'DNS query refused',
292 FORMERR => 'format error',
293 NOTIMP => 'not implemented');
294 if(defined($dnsrespcodes{$response})) {
295 return sprintf('%s (%s)',$response,$dnsrespcodes{$response});
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 # $error : DNS response code
307 # \$log : reference to the log (to be printed out via -l)
309 # \$log will be changed
310 sub print_dns_result {
311 my ($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 $$logr .= sprintf("%s DNS record(s):\n",$type);
316 printf(" No %s records found for %s: %s\n",$type,$domain,parse_dns_reply($error)) if !($options{'q'});
317 $$logr .= sprintf("No %s records found: %s\n",$type,parse_dns_reply($error));
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 # $message: SMTP status message
330 # \$log will be changed
332 my($smtpr,$recipient,$logr)=@_;
333 $$logr .= sprintf("RCPT TO:<%s>\n",$recipient);
335 $$smtpr->to($recipient);
337 log_smtp_reply($logr,$$smtpr->code,$$smtpr->message);
338 $success = analyze_smtp_reply($$smtpr->code,$$smtpr->message);
341 $$logr .= "---Connection failure---\n";
343 return ($success,$$smtpr->code,$$smtpr->message);
346 ################################ log_smtp_reply ################################
347 # log result of SMTP command
348 # IN : \$log : reference to the log (to be printed out via -l)
349 # $code : SMTP status code
350 # @message : SMTP status message
352 # \$log will be changed
354 my($logr,$code,@message)=@_;
355 $$logr .= sprintf('%s %s',$code,join('- ',@message));
359 ############################### analyze_smtp_reply ##############################
360 # analyze SMTP response codes and messages
361 # IN : $code : SMTP status code
362 # @message : SMTP status message
363 # OUT: exit code (0 for false, 1 for true, -1 for tempfail)
364 sub analyze_smtp_reply {
365 my($code,@message)=@_;
366 my $type = substr($code, 0, 1);
369 } elsif ($type == 5) {
371 } elsif ($type == 4) {
377 ############################## connection_failed ###############################
378 # print failure message and return status 1
379 # IN : @message : SMTP status message
381 sub connection_failed {
383 print " ! Connection failed or other temporary failure.\n" if !($options{'q'});
384 printf(" %s\n",join(' ',@message)) if @message;
390 ################################ Documentation #################################
394 checkmail - check deliverability of a mail address
398 B<checkmail> [B<-Vhqlr>] [B<-m> I<host>] [-s I<sender>] [-e I<EHLO>] I<address>|B<-f> I<file>
418 Mail::Address I<(CPAN)>
430 Furthermore you'll need a working DNS installation.
434 checkmail checks the vailidity / deliverability of a mail address.
435 You may submit just one address as the last argument or a file
436 containing one address on each line using the B<-f> option.
440 For the time being, all configuration is done in the script. You have
441 to set the following elements of the %config hash:
445 =item B<$config{'helo'}>
447 The hostname to be used for I<HELO> or I<EHLO> in the SMTP dialog.
449 =item B<$config{'from'}>
451 The sender address to be used for I<MAIL FROM> while testing.
452 May be empty ('') to set '<>' as MAIL FROM.
456 You may override that configuration by using the B<-e> and B<-s>
457 command line options.
461 After configuring the script you may run your first test with
463 checkmail user@example.org
465 B<checkmail> will check the address for syntactic validity. If the
466 address is valid, it will try to determine the mail exchanger(s) (MX)
467 responsible for I<example.org> by querying the DNS for the respective
468 MX records and then try to connect via SMTP (on port 25) to each of
469 them in order of precedence (if necessary). It will run through the
470 SMTP dialog until just before the I<DATA> stage, i.e. doing I<EHLO>,
471 I<MAIL FROM> and I<RCPT TO>. If no MX is defined, B<checkmail> will
472 fall back to the I<example.org> host itself, provided there is at
473 least one A record defined in the DNS. CNAMEs will be accepted and
474 resolved here. If there are neither MX nor A records for
475 I<example.org>, mail is not deliverable and B<checkmail> will fail
476 accordingly. If no host can be reached, B<checkmail> will fail,
477 too. Finally B<checkmail> will fail if mail to the given recipient
478 is not accepted by the respective host.
480 If B<checkmail> fails, you'll not be able to deliver mail to that
481 address - at least not using the configured sender address and from
482 the host you're testing from. However, the opposite is not true: a
483 mail you send may still not be delivered even if a test via
484 B<checkmail> succeeds. The receiving entity may reject your mail after
485 the I<DATA> stage, due to content checking or without any special
486 reason, or it may even drop, filter or bounce your mail after finally
487 accepting it. There is no way to be sure a mail will be accepted short
488 of sending a real mail to the address in question.
490 You may, however, try to detect hosts that will happily accept any and
491 all recipient in the SMTP dialog and just reject your mail later on,
492 for example to defeat exactly the kind of check you try to do.
493 B<checkmail> will do that by submitting a recipient address that is
494 known to be invalid; if that address is accepted, too, you'll know
495 that you can't reliably check the validity of any address on that
496 host. You can force that check by using the B<-r> option.
498 If you don't want to see just the results of your test, you can get a
499 B<complete log> of the SMTP dialog by using the B<-l> option. That may be
500 helpful to test for temporary failure conditions.
502 On the other hand you may use the B<-q> option to suppress all output;
503 B<checkmail> will then terminate with one of the following B<exit
510 address(es) seem/seems to be valid
514 temporary error (connection failure or temporary failure)
522 address cannot reliably be checked (test using B<-r> failed)
526 You can do B<batch processing> using B<-f> and submitting a file with
527 one address on each line. In that case the exit status is set to the
528 highest value generated by testing all addresses, i.e. it is set to
529 B<0> if and only if no adress failed, but to B<2> if even one address
530 failed and to B<3> if even one addresses couldn't reliably be checked.
532 And finally you can B<suppress DNS lookups> for MX and A records and
533 just force B<checkmail> to connect to a particular host using the
536 B<Please note:> You shouldn't try to validate addresses while working
537 from a dial-up or blacklisted host. If in doubt, use the B<-l> option
538 to have a closer look on the SMTP dialog yourself.
540 B<Please note:> To avoid shell expansion on addresses you submit to
541 B<checkmail>, use B<batch processing>.
547 =item B<-V> (version)
549 Print out version and copyright information on B<checkmail> and exit.
553 Print this man page and exit.
557 Suppress output and just terminate with a specific exit status.
561 Log and print out the whole SMTP dialog.
563 =item B<-r> (random address)
565 Also try a reliably invalid address to catch hosts that try undermine
566 address verification.
568 =item B<-m> I<host> (MX to use)
570 Force a connection to I<host> to check deliverability to that
571 particular host irrespective of DNS entries. For example:
573 checkmail -m test.host.example user@domain.example
575 =item B<-s> I<sender> (value for MAIL FROM)
577 Override configuration and use I<sender> for MAIL FROM.
579 =item B<-e> I<EHLO> (value for EHLO)
581 Override configuration and use I<EHLO> for EHLO.
583 =item B<-f> I<file> (file)
585 Process all addresses from I<file> (one on each line).
591 Just copy checkmail to some directory and get started.
593 You can run your first test with
595 checkmail user@example.org
599 See documentation of I<Net::DNS::Resolver>.
605 =item F<checkmail.pl>
613 Please report any bugs or feature request to the author or use the
614 bug tracker at L<http://bugs.th-h.de/>!
618 L<http://th-h.de/download/scripts.php> will have the current
619 version of this program.
621 This program is maintained using the Git version control system. You
622 may clone L<git://code.th-h.de/mail/checkmail.git> to check out the
623 current development tree or browse it on the web via
624 L<http://code.th-h.de/?p=mail/checkmail.git>.
628 Thomas Hochstein <thh@inter.net>
630 =head1 COPYRIGHT AND LICENSE
632 Copyright (c) 2002-2016 Thomas Hochstein <thh@inter.net>
634 This program is free software; you may redistribute it and/or modify it
635 under the same terms as Perl itself.