Cara memeriksa apakah smtp berfungsi dari commandline (Linux)

Satu-satunya hal tentang menggunakan telnet untuk menguji postfix, atau SMTP lainnya, adalah Anda harus mengetahui perintah dan sintaks. Sebagai gantinya, gunakan saja swaks :)

example@unixlinux.online:~$ 
example@unixlinux.online:~$ mail -f Maildir
"/home/thufir/Maildir": 4 messages
>    1 example@unixlinux.online                   15/553   test Mon, 30 Dec 2013 10:15:12 -0800
     2 example@unixlinux.online                   15/581   test Mon, 30 Dec 2013 10:15:55 -0800
     3 example@unixlinux.online                   15/581   test Mon, 30 Dec 2013 10:29:57 -0800
     4 example@unixlinux.online                   15/581   test Mon, 30 Dec 2013 11:54:16 -0800
? q
Held 4 messages in /home/thufir/Maildir
example@unixlinux.online:~$ 
example@unixlinux.online:~$ swaks --to example@unixlinux.online
=== 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:<example@unixlinux.online>
<-  250 2.1.0 Ok
 -> RCPT TO:<example@unixlinux.online>
<-  250 2.1.5 Ok
 -> DATA
<-  354 End data with <CR><LF>.<CR><LF>
 -> Date: Mon, 30 Dec 2013 14:33:17 -0800
 -> To: example@unixlinux.online
 -> From: example@unixlinux.online
 -> 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.
example@unixlinux.online:~$ 
example@unixlinux.online:~$ mail -f Maildir
"/home/thufir/Maildir": 5 messages 1 new
     1 example@unixlinux.online                   15/553   test Mon, 30 Dec 2013 10:15:12 -0800
     2 example@unixlinux.online                   15/581   test Mon, 30 Dec 2013 10:15:55 -0800
     3 example@unixlinux.online                   15/581   test Mon, 30 Dec 2013 10:29:57 -0800
     4 example@unixlinux.online                   15/581   test Mon, 30 Dec 2013 11:54:16 -0800
>N   5 example@unixlinux.online                   15/581   test Mon, 30 Dec 2013 14:33:17 -0800
? 5
Return-Path: <example@unixlinux.online>
X-Original-To: example@unixlinux.online
Delivered-To: example@unixlinux.online
Received: from dur.bounceme.net (localhost [127.0.0.1])
    by dur.bounceme.net (Postfix) with ESMTP id 52D162C3EFF
    for <example@unixlinux.online>; Mon, 30 Dec 2013 14:33:17 -0800 (PST)
Date: Mon, 30 Dec 2013 14:33:17 -0800
To: example@unixlinux.online
From: example@unixlinux.online
Subject: test Mon, 30 Dec 2013 14:33:17 -0800
X-Mailer: swaks v20130209.0 jetmore.org/john/code/swaks/
Message-Id: <example@unixlinux.online>

This is a test mailing

New mail has arrived.
? q
Held 5 messages in /home/thufir/Maildir
example@unixlinux.online:~$ 

Itu hanya satu perintah mudah.

[example@unixlinux.online tmp]# mail -v example@unixlinux.online
Subject: Test
Hello world
Cc:  <Ctrl+D>

example@unixlinux.online 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:<example@unixlinux.online> SIZE=46
250 2.1.0 <example@unixlinux.online>... Sender ok
>>> RCPT To:<example@unixlinux.online>
>>> DATA
250 2.1.5 <example@unixlinux.online>... Recipient ok
354 Enter mail, end with "." on a line by itself
>>> .
250 2.0.0 q7NEneju002633 Message accepted for delivery
example@unixlinux.online Sent (q7NEneju002633 Message accepted for delivery)
Closing connection to [127.0.0.1]
>>> QUIT
221 2.0.0 piwik-dev.example.com closing connection

Sintaks untuk membuat koneksi jaringan mentah menggunakan telnet adalah ini:

telnet {domain_name} {port_number}

Jadi telnet ke server SMTP Anda seperti

telnet smtp.mydomain.example 25

Dan salin dan tempel di bawah ini

helo client.mydomain.example
mail from:<example@unixlinux.online>
rcpt to:<example@unixlinux.online>
data
From: example@unixlinux.online
Subject: test mail from command line

this is test number 1
sent from linux box
.
quit

Catatan : Jangan lupa "." di bagian akhir yang mewakili akhir pesan. Baris "keluar" keluar mengakhiri sesi.