How to check if smtp is working from commandline (Linux)

I have a SMTP-server, for the purpose of this question lets call it: smtp.mydomain.com.

How do i check if the SMTP-server is in working? Can I send emails manually from Linux commandline?

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:<sender@mydomain.com>
rcpt to:<to_email@mydomain.com>
data
From: test@mydomain.com
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 thufir@dur.bouncem                   15/553   test Mon, 30 Dec 2013 10:15:12 -0800
     2 thufir@dur.bouncem                   15/581   test Mon, 30 Dec 2013 10:15:55 -0800
     3 thufir@dur.bouncem                   15/581   test Mon, 30 Dec 2013 10:29:57 -0800
     4 thufir@dur.bouncem                   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:<thufir@dur.bounceme.net>
<-  250 2.1.0 Ok
 -> RCPT TO:<thufir@dur.bounceme.net>
<-  250 2.1.5 Ok
 -> DATA
<-  354 End data with <CR><LF>.<CR><LF>
 -> Date: Mon, 30 Dec 2013 14:33:17 -0800
 -> To: thufir@dur.bounceme.net
 -> From: thufir@dur.bounceme.net
 -> 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 thufir@dur.bouncem                   15/553   test Mon, 30 Dec 2013 10:15:12 -0800
     2 thufir@dur.bouncem                   15/581   test Mon, 30 Dec 2013 10:15:55 -0800
     3 thufir@dur.bouncem                   15/581   test Mon, 30 Dec 2013 10:29:57 -0800
     4 thufir@dur.bouncem                   15/581   test Mon, 30 Dec 2013 11:54:16 -0800
>N   5 thufir@dur.bouncem                   15/581   test Mon, 30 Dec 2013 14:33:17 -0800
? 5
Return-Path: <thufir@dur.bounceme.net>
X-Original-To: thufir@dur.bounceme.net
Delivered-To: thufir@dur.bounceme.net
Received: from dur.bounceme.net (localhost [127.0.0.1])
	by dur.bounceme.net (Postfix) with ESMTP id 52D162C3EFF
	for <thufir@dur.bounceme.net>; Mon, 30 Dec 2013 14:33:17 -0800 (PST)
Date: Mon, 30 Dec 2013 14:33:17 -0800
To: thufir@dur.bounceme.net
From: thufir@dur.bounceme.net
Subject: test Mon, 30 Dec 2013 14:33:17 -0800
X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
Message-Id: <20131230223317.52D162C3EFF@dur.bounceme.net>

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/