Normally, to check if my server smtp connection alive, I just do telnet to port 25 from my workstation. if the smtp banner displayed, it means that the connection to the smtp server is good. I have done this for years. 😆
$ telnet smtp.example.com 25 Trying xxx.xxx.xx.xxx... Connected to xxx.xxx.xx.x. Escape character is '^]'. 220 smtp.example.com ESMTP Postfix ehlo host.example.com 250-smtp.example.com 250-PIPELINING 250-SIZE 52428800 250-ETRN 250-STARTTLS 250-AUTH LOGIN PLAIN 250-AUTH=LOGIN PLAIN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN quit 221 2.0.0 Bye Connection closed by foreign host.
Although many tools that are deliberately created for this purpose, still, I prefer just using telnet to port 25. I have made a simple perl script, with the intention that the things I do for years manually can be done automatically.
Modules required:
This is the perl script
#!/usr/bin/perl -w
use strict;
use warnings;
use Net::SMTP;
use Time::HiRes qw(gettimeofday);
my $start = gettimeofday();
my $smtp = Net::SMTP->new("$ARGV[0]",
Hello => 'my.host.com',
Timeout => 60) or die "Cannot connect to remote smtp: $@";
my $banner = $smtp->banner;
my $end = gettimeofday();
my $delta = ($end - $start);
printf "%s", $banner;
printf "%s takes : %.3f seconds to get connected\n", $ARGV[0], $delta;
$smtp->quit;
exit 0;
This is an example of how the script works
$ ./smtp-check.pl aspmx.l.google.com mx.google.com ESMTP w15si5875063ibh.43 aspmx.l.google.com takes : 1.807 seconds to get connected $ ./smtp-check.pl h.mx.mail.yahoo.com mta1186.mail.mud.yahoo.com ESMTP YSmtp service ready h.mx.mail.yahoo.com takes : 1.176 seconds to get connected $ ./smtp-check.pl mail.cloud9.net english-breakfast.cloud9.net ESMTP Postfix mail.cloud9.net takes : 2.622 seconds to get connected
That’s all for now.