Type telnet MAILSERVER 25 (replace MAILSERVER with your mail server (SMTP) which may be something like server.domain.com or mail.yourdomain.com). Press Enter. If that port is blocked, you will receive a connection error.
If you have access to the system and you want to check whether it's blocked or open, you can use netstat -tuplen | grep 25 to see if the service is on and is listening to the IP address or not. You can also try to use iptables -nL | grep <port number> to see if there is any rule set by your firewall.
Syntax for establishing a raw network connection using telnet is this:
telnet {domain_name} {port_number}
So telnet to your smtp server like
telnet smtp.mydomain.com 25
And copy and paste the below
helo client.mydomain.com
mail from:<[email protected]>
rcpt to:<[email protected]>
data
From: [email protected]
Subject: test mail from command line
this is test number 1
sent from linux box
.
quit
Note : Do not forgot the "." at the end which represents the end of the message. The "quit" line exits ends the session.
The only thing about using telnet to test postfix, or other SMTP, is that you have to know the commands and syntax. Instead, just use swaks :)
thufir@dur:~$
thufir@dur:~$ mail -f Maildir
"/home/thufir/Maildir": 4 messages
> 1 [email protected] 15/553 test Mon, 30 Dec 2013 10:15:12 -0800
2 [email protected] 15/581 test Mon, 30 Dec 2013 10:15:55 -0800
3 [email protected] 15/581 test Mon, 30 Dec 2013 10:29:57 -0800
4 [email protected] 15/581 test Mon, 30 Dec 2013 11:54:16 -0800
? q
Held 4 messages in /home/thufir/Maildir
thufir@dur:~$
thufir@dur:~$ swaks --to [email protected]
=== Trying dur.bounceme.net:25...
=== Connected to dur.bounceme.net.
<- 220 dur.bounceme.net ESMTP Postfix (Ubuntu)
-> EHLO dur.bounceme.net
<- 250-dur.bounceme.net
<- 250-PIPELINING
<- 250-SIZE 10240000
<- 250-VRFY
<- 250-ETRN
<- 250-STARTTLS
<- 250-ENHANCEDSTATUSCODES
<- 250-8BITMIME
<- 250 DSN
-> MAIL FROM:<[email protected]>
<- 250 2.1.0 Ok
-> RCPT TO:<[email protected]>
<- 250 2.1.5 Ok
-> DATA
<- 354 End data with <CR><LF>.<CR><LF>
-> Date: Mon, 30 Dec 2013 14:33:17 -0800
-> To: [email protected]
-> From: [email protected]
-> Subject: test Mon, 30 Dec 2013 14:33:17 -0800
-> X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
->
-> This is a test mailing
->
-> .
<- 250 2.0.0 Ok: queued as 52D162C3EFF
-> QUIT
<- 221 2.0.0 Bye
=== Connection closed with remote host.
thufir@dur:~$
thufir@dur:~$ mail -f Maildir
"/home/thufir/Maildir": 5 messages 1 new
1 [email protected] 15/553 test Mon, 30 Dec 2013 10:15:12 -0800
2 [email protected] 15/581 test Mon, 30 Dec 2013 10:15:55 -0800
3 [email protected] 15/581 test Mon, 30 Dec 2013 10:29:57 -0800
4 [email protected] 15/581 test Mon, 30 Dec 2013 11:54:16 -0800
>N 5 [email protected] 15/581 test Mon, 30 Dec 2013 14:33:17 -0800
? 5
Return-Path: <[email protected]>
X-Original-To: [email protected]
Delivered-To: [email protected]
Received: from dur.bounceme.net (localhost [127.0.0.1])
by dur.bounceme.net (Postfix) with ESMTP id 52D162C3EFF
for <[email protected]>; Mon, 30 Dec 2013 14:33:17 -0800 (PST)
Date: Mon, 30 Dec 2013 14:33:17 -0800
To: [email protected]
From: [email protected]
Subject: test Mon, 30 Dec 2013 14:33:17 -0800
X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
Message-Id: <[email protected]>
This is a test mailing
New mail has arrived.
? q
Held 5 messages in /home/thufir/Maildir
thufir@dur:~$
It's just one easy command.
[root@piwik-dev tmp]# mail -v root@localhost
Subject: Test
Hello world
Cc: <Ctrl+D>
root@localhost... Connecting to [127.0.0.1] via relay...
220 piwik-dev.example.com ESMTP Sendmail 8.13.8/8.13.8; Thu, 23 Aug 2012 10:49:40 -0400
>>> EHLO piwik-dev.example.com
250-piwik-dev.example.com Hello localhost.localdomain [127.0.0.1], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-DELIVERBY
250 HELP
>>> MAIL From:<[email protected]> SIZE=46
250 2.1.0 <[email protected]>... Sender ok
>>> RCPT To:<[email protected]>
>>> DATA
250 2.1.5 <[email protected]>... Recipient ok
354 Enter mail, end with "." on a line by itself
>>> .
250 2.0.0 q7NEneju002633 Message accepted for delivery
root@localhost... Sent (q7NEneju002633 Message accepted for delivery)
Closing connection to [127.0.0.1]
>>> QUIT
221 2.0.0 piwik-dev.example.com closing connection
Not sure if this help or not but this is a command line tool which let you simply send test mails from a SMTP server priodically. http://code.google.com/p/woodpecker-tester/
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