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'
23 ################################### Modules ####################################
30 ################################# Main program #################################
32 $Getopt::Std::STANDARD_HELP_VERSION = 1;
33 my $myself = basename($0);
35 # read commandline options
37 getopts('Vhqlrf:m:', \%options);
41 print "$myself v $VERSION\nCopyright (c) 2010 Thomas Hochstein <thh\@inter.net>\n";
42 print "This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.\n";
46 # -h: feed myself to perldoc
52 # display usage information if neither -f nor an address are present
53 if (!$options{'f'} and !$ARGV[0]) {
54 print "Usage: $myself [-hqlr] [-m <host>] <address>|-f <file>\n";
55 print "Options: -V display copyright and version\n";
56 print " -h show documentation\n";
57 print " -q quiet (no output, just exit with 0/1/2/3)\n";
58 print " -l extended logging\n";
59 print " -r test random address to verify verification\n";
60 print " -m <host> no DNS lookup, just test this host\n";
61 print " <address> mail address to check\n\n";
62 print " -f <file> parse file (one address per line)\n";
66 # -f: open file and read addresses to @adresses
69 if (-e $options{'f'}) {
70 open FILE, "<$options{'f'}" or die("$myself ERROR: Could not open file $options{'f'} for reading: $!");
72 die("$myself ERROR: File $options{'f'} does not exist!\n");
79 # fill @adresses with single address to check
81 push(@addresses,$ARGV[0]);
84 # loop over each address and test it
85 my (%targets,$curstat,$status,$log,$message);
86 foreach (@addresses) {
88 (undef,my $domain) = splitaddress($address);
89 printf(" * Testing %s ...\n",$address) if !($options{'q'});
90 $log .= "\n===== BEGIN $address =====\n";
91 # get list of target hosts or take host forced via -m
93 %targets = %{gettargets($domain,\$log)};
95 $message = sprintf("Connection to %s forced by -m.\n",$options{'m'});
97 print " $message" if !($options{'q'});
98 # just one target host with preference 0
99 $targets{$options{'m'}} = 0;
102 $curstat = checkaddress($address,\%targets,\$log);
105 $message = 'DNS lookup failure';
106 printf(" > Address is INVALID (%s).\n",$message) if !($options{'q'});
107 $log .= $message . '.';
109 $log .= "====== END $address ======\n";
110 $status = $curstat if (!defined($status) or $curstat > $status);
113 print $log if ($options{'l'});
115 # status 0: valid / batch processing
116 # 1: connection failed or temporary failure
119 #D print "\n-> EXIT $status\n";
122 ################################## gettargets ##################################
123 # get mail exchanger(s) or A record(s) for a domain
124 # IN : $domain: domain to query the DNS for
125 # OUT: \%targets: reference to a hash containing a list of target hosts
127 my ($domain,$logr) = @_;
129 my $resolver = Net::DNS::Resolver->new(udp_timeout => 15, tcp_timeout => 15);
132 # get MX record(s) as a list sorted by preference
133 if (my @mxrr = mx($resolver,$domain)) {
134 print_dns_result($domain,'MX',scalar(@mxrr),undef,$logr);
135 foreach my $rr (@mxrr) {
136 $targets{$rr->exchange} = $rr->preference;
137 $$logr .= sprintf("(%d) %s\n",$rr->preference,$rr->exchange);
139 # no MX record found; log and try A record(s)
141 print_dns_result($domain,'MX',undef,$resolver->errorstring,$logr);
142 print(" Falling back to A record ...\n") if !($options{'q'});
144 if (my $query = $resolver->query($domain,'A','IN')) {
145 print_dns_result($domain,'A',$query->header->ancount,undef,$logr);
146 foreach my $rr ($query->answer) {
147 $targets{$rr->address} = 0;
148 $$logr .= sprintf("- %s\n",$rr->address);
150 # no A record found either; log and fail
152 print_dns_result($domain,'A',undef,$resolver->errorstring,$logr);
153 printf(" %s has neither MX nor A records - mail cannot be delivered.\n",$domain) if !($options{'q'});
159 ################################# checkaddress #################################
160 # test address for deliverability
161 # IN : $address: adress to be tested
162 # \%targets: reference to a hash containing a list of MX hosts
163 # \$log : reference to the log (to be printed out via -l)
165 # \$log will be changed
167 my ($address,$targetsr,$logr) = @_;
168 my %targets = %{$targetsr};
170 # walk %targets in order of preference
171 foreach my $host (sort { $targets{$a} <=> $targets{$b} } keys %targets) {
172 printf(" / Trying %s (%s) with %s\n",$host,$targets{$host} || 'A',$address) if !($options{'q'});
173 $$logr .= sprintf("%s:\n%s\n",$host,"-" x (length($host)+1));
174 $status = checksmtp($address,$host,$logr);
175 last if ($status != 1);
180 ################################### checksmtp ##################################
181 # connect to a remote machine on port 25 and test deliverability of a mail
182 # address by doing the SMTP dialog until RCPT TO stage
183 # IN : $address: address to test
184 # $target : target host
185 # \$log : reference to the log (to be printed out via -l)
186 # OUT: .........: reference to a hash containing a list of target hosts
187 # \$log will be changed
189 my ($address,$target,$logr) = @_;
191 # start SMTP connection
192 if (my $smtp = Net::SMTP->new($target,Hello => $config{'helo'},Timeout => 30)) {
193 $$logr .= $smtp->banner; # Net::SMTP doesn't seem to support multiline greetings.
194 $$logr .= "EHLO $config{'helo'}\n";
195 log_smtp_reply($logr,$smtp->code,$smtp->message);
196 $smtp->mail($config{'from'});
197 $$logr .= "MAIL FROM:<$config{'from'}>\n";
198 log_smtp_reply($logr,$smtp->code,$smtp->message);
200 my ($success,$code,@message) = try_rcpt_to(\$smtp,$address,$logr);
201 # connection failure?
203 $status = connection_failed(@message);
204 # delivery attempt was successful?
206 # -r: try random address (which should be guaranteed to be invalid)
208 (undef,my $domain) = splitaddress($address);
209 my ($success,$code,@message) = try_rcpt_to(\$smtp,create_rand_addr($domain),$logr);
210 # connection failure?
212 $status = connection_failed(@message);
213 # verification impossible?
216 print " > Address verificaton impossible. You'll have to send a test mail ...\n" if !($options{'q'});
219 # if -r is not set or status was not set to 3: valid address
220 if (!defined($status)) {
222 print " > Address is valid.\n" if !($options{'q'});
224 # delivery attempt failed?
227 print " > Address is INVALID:\n" if !($options{'q'});
228 print ' ' . join(' ',@message) if !($options{'q'});
230 # terminate SMTP connection
233 log_smtp_reply($logr,$smtp->code,$smtp->message);
235 # SMTP connection failed / timeout
236 $status = connection_failed();
237 $$logr .= "---Connection failure---\n";
242 ################################# splitaddress #################################
243 # split mail address into local and domain part
244 # IN : $address: a mail address
245 # OUT: $local : local part
246 # $domain: domain part
249 (my $lp = $address) =~ s/^([^@]+)@.*/$1/;
250 (my $domain = $address) =~ s/[^@]+\@(\S*)$/$1/;
251 return ($lp,$domain);
254 ############################### create_rand_addr ###############################
255 # create a random mail address
256 # IN : $domain: the domain part
257 # OUT: $address: the address
258 sub create_rand_addr {
260 my $allowed = 'ABCDEFGHJKLMNPQRSTUVWXYZabcdefghjkmnpqrstuvwxyz23456789-+_=';
262 while (length($address) < 15) {
263 $address .= substr($allowed, (int(rand(length($allowed)))),1);
265 return ($address.'@'.$domain);
268 ################################ parse_dns_reply ###############################
269 # parse DNS response codes and return code and description
270 # IN : $response: a DNS response code
271 # OUT: "$response ($desciption)"
272 sub parse_dns_reply {
274 my %dnsrespcodes = (NOERROR => 'empty response',
275 NXDOMAIN => 'non-existent domain',
276 SERVFAIL => 'DNS server failure',
277 REFUSED => 'DNS query refused',
278 FORMERR => 'format error',
279 NOTIMP => 'not implemented');
280 if(defined($dnsrespcodes{$response})) {
281 return sprintf('%s (%s)',$response,$dnsrespcodes{$response});
287 ############################### print_dns_result ###############################
288 # print and log result of DNS query
289 # IN : $domain: domain the DNS was queried for
290 # $type : record type (MX, A, ...)
291 # $count : number of records found
292 # $error : DNS response code
293 # \$log : reference to the log (to be printed out via -l)
295 # \$log will be changed
296 sub print_dns_result {
297 my ($domain,$type,$count,$error,$logr) = @_;
298 if (defined($count)) {
299 printf(" %d %s record(s) found for %s\n",$count,$type,$domain) if !($options{'q'});
300 $$logr .= sprintf("%s DNS record(s):\n",$type);
302 printf(" No %s records found for %s: %s\n",$type,$domain,parse_dns_reply($error)) if !($options{'q'});
303 $$logr .= sprintf("No %s records found: %s\n",$type,parse_dns_reply($error));
308 ################################## try_rcpt_to #################################
309 # send RCPT TO and return replies
310 # IN : \$smtp : a reference to an SMTP object
311 # $recipient: a mail address
312 # \$log : reference to the log (to be printed out via -l)
313 # OUT: $success: exit code (0 for false, 1 for true, -1 for tempfail)
314 # $code : SMTP status code
315 # $message: SMTP status message
316 # \$log will be changed
318 my($smtpr,$recipient,$logr)=@_;
319 $$logr .= sprintf("RCPT TO:<%s>\n",$recipient);
321 $$smtpr->to($recipient);
323 log_smtp_reply($logr,$$smtpr->code,$$smtpr->message);
324 $success = analyze_smtp_reply($$smtpr->code,$$smtpr->message);
327 $$logr .= "---Connection failure---\n";
329 return ($success,$$smtpr->code,$$smtpr->message);
332 ################################ log_smtp_reply ################################
333 # log result of SMTP command
334 # IN : \$log : reference to the log (to be printed out via -l)
335 # $code : SMTP status code
336 # @message : SMTP status message
338 # \$log will be changed
340 my($logr,$code,@message)=@_;
341 $$logr .= sprintf('%s %s',$code,join('- ',@message));
345 ############################### analyze_smtp_reply ##############################
346 # analyze SMTP response codes and messages
347 # IN : $code : SMTP status code
348 # @message : SMTP status message
349 # OUT: exit code (0 for false, 1 for true, -1 for tempfail)
350 sub analyze_smtp_reply {
351 my($code,@message)=@_;
352 my $type = substr($code, 0, 1);
355 } elsif ($type == 5) {
357 } elsif ($type == 4) {
363 ############################## connection_failed ###############################
364 # print failure message and return status 1
365 # IN : @message : SMTP status message
367 sub connection_failed {
369 print " ! Connection failed or other temporary failure.\n" if !($options{'q'});
370 printf(" %s\n",join(' ',@message)) if @message;
376 ################################ Documentation #################################
380 checkmail - check deliverability of a mail address
384 B<checkmail> [B<-Vhqlr>] [B<-m> I<host>] I<address>|B<-f> I<file>
412 Furthermore you'll need a working DNS installation.
416 checkmail checks the vailidity / deliverability of a mail address.
417 You may submit just one address as the last argument or a file
418 containing one address on each line using the B<-f> option.
422 For the time being, all configuration is done in the script. You have
423 to set the following elements of the %config hash:
427 =item B<$config{'helo'}>
429 The hostname to be used for I<HELO> or I<EHLO> in the SMTP dialog.
431 =item B<$config{'from'}>
433 The sender address to be used for I<MAIL FROM> while testing.
439 After configuring the script you may run your first test with
441 checkmail user@example.org
443 B<checkmail> will try to determine the mail exchanger(s) (MX)
444 responsible for I<example.org> by querying the DNS for the respective
445 MX records and then try to connect via SMTP (on port 25) to each of
446 them in order of precedence (if necessary). It will run through the
447 SMTP dialog until just before the I<DATA> stage, i.e. doing I<EHLO>,
448 I<MAIL FROM> and I<RCPT TO>. If no MX is defined, B<checkmail> will
449 fall back to the I<example.org> host itself, provided there is at
450 least one A record defined in the DNS. If there are neither MX nor A
451 records for I<example.org>, mail is not deliverable and B<checkmail>
452 will fail accordingly. If no host can be reached, B<checkmail> will
453 fail, too. Finally B<checkmail> will fail if mail to the given
454 recipient is not accepted by the respective host.
456 If B<checkmail> fails, you'll not be able to deliver mail to that
457 address - at least not using the configured sender address and from
458 the host you're testing from. However, the opposite is not true: a
459 mail you send may still not be delivered even if a test via
460 B<checkmail> succeeds. The receiving entity may reject your mail after
461 the I<DATA> stage, due to content checking or without any special
462 reason, or it may even drop, filter or bounce your mail after finally
463 accepting it. There is no way to be sure a mail will be accepted short
464 of sending a real mail to the address in question.
466 You may, however, try to detect hosts that will happily accept any and
467 all recipient in the SMTP dialog and just reject your mail later on,
468 for example to defeat exactly the kind of check you try to do.
469 B<checkmail> will do that by submitting a recipient address that is
470 known to be invalid; if that address is accepted, too, you'll know
471 that you can't reliably check the validity of any address on that
472 host. You can force that check by using the B<-r> option.
474 If you don't want to see just the results of your test, you can get a
475 B<complete log> of the SMTP dialog by using the B<-l> option. That may be
476 helpful to test for temporary failure conditions.
478 On the other hand you may use the B<-q> option to suppress all output;
479 B<checkmail> will then terminate with one of the following B<exit
486 address(es) seem/seems to be valid
490 temporary error (connection failure or temporary failure)
498 address cannot reliably be checked (test using B<-r> failed)
502 You can do B<batch processing> using B<-f> and submitting a file with
503 one address on each line. In that case the exit status is set to the
504 highest value generated by testing all addresses, i.e. it is set to
505 B<0> if and only if no adress failed, but to B<2> if even one address
506 failed and to B<3> if even one addresses couldn't reliably be checked.
508 And finally you can B<suppress DNS lookups> for MX and A records and
509 just force B<checkmail> to connect to a particular host using the
512 B<Please note:> You shouldn't try to validate addresses while working
513 from a dial-up or blacklisted host. If in doubt, use the B<-l> option
514 to have a closer look on the SMTP dialog yourself.
520 =item B<-V> (version)
522 Print out version and copyright information on B<checkmail> and exit.
526 Print this man page and exit.
530 Suppress output and just terminate with a specific exit status.
534 Log and print out the whole SMTP dialog.
536 =item B<-r> (random address)
538 Also try a reliably invalid address to catch hosts that try undermine
539 address verification.
541 =item B<-m> I<host> (MX to use)
543 Force a connection to I<host> to check deliverability to that
544 particular host irrespective of DNS entries. For example:
546 checkmail -m test.host.example user@domain.example
548 =item B<-f> I<file> (file)
550 Process all addresses from I<file> (one on each line).
556 Just copy checkmail to some directory and get started.
558 You can run your first test with
560 checkmail user@example.org
564 See documentation of I<Net::DNS::Resolver>.
570 =item F<checkmail.pl>
578 Please report any bugs or feature request to the author or use the
579 bug tracker at L<http://bugs.th-h.de/>!
583 L<http://th-h.de/download/scripts.php> will have the current
584 version of this program.
586 This program is maintained using the Git version control system. You
587 may clone L<git://code.th-h.de/mail/checkmail.git> to check out the
588 current development tree or browse it on the web via
589 L<http://code.th-h.de/?p=mail/checkmail.git>.
593 Thomas Hochstein <thh@inter.net>
595 =head1 COPYRIGHT AND LICENSE
597 Copyright (c) 2002-2010 Thomas Hochstein <thh@inter.net>
599 This program is free software; you may redistribute it and/or modify it
600 under the same terms as Perl itself.