How to test/diagnose SMTP mail connections using the SMTP Test Tool.
Posted by David Rutherford on 19 November 2012 03:44 PM

The SMTP Test Tool is used to diagnose an SMTP protocol connection between your PerfectMail™ server and another mail server. SMTP (S M T P) stands for Simple Mail Transfer Protocol. It is the protocol for sending e-mail messages between servers.

The information used to test the SMTP protocol are similar to what you would use for sending an e-mail. In fact the tool will actually send an e-mail to the recipient you choose. The important thing to note is that you must specify the IP address of the mail server you want to connect to. During the process of sending this e-mail the actual SMTP commands used during communication will be displayed.

Options for using this tool are as follows:

  • Server IP - The IP address of the mail server you want to connect to;
  • Port - The port number (25 by default) that you want to connect to;
  • From - The "from" e-mail address (may be blank);
  • To - The "to" or "recipient" e-mail address; you may provide multiple e-mail addresses separated by commas ',';
  • Subject - An optional subject line;
  • Message - Simple message content. (Text only. Keep it simple.)

Click the "Send" button to run the test. The actual SMTP commands will be displayed in the output box. Data sent from your PerfectMail server to the specified mail host will be prefaced with ">>", data received from the specified mail host will be prefaced with "<<".

Each line sent from your PerfectMail server will be responded to with a three digit return value:

  • 200, 300 series numbers (e.g. 220, 250, 354, etc.) denote normal response codes.
  • 400 series numbers (e.g. 421) denote temporary delivery errors; a recipient or the message could not be accepted/delivered at the current time, but you should try to send the message again.
  • 500 series number (e.g. 550) denote permanent delivery errors; a recipient or the message will not be accepted/delivered.


[+] Connected to 25
<< 220 ESMTP Sendmail 8.14.2/8.14.2; Mon, 19 Nov 2012 12:28:20 -0500
>> HELO localhost.localdomain
<< 250 Hello remotehost.localdomain [], pleased to meet you
>> MAIL FROM: <>
<< 250 2.1.0 <>... Sender ok
>> RCPT TO: <>
<< 250 2.1.5 <>... Recipient ok
<< 354 Enter mail, end with "." on a line by itself
>> To: <>
Subject: Testing connection
Date: Mon, 19 Nov 2012 12:28:22 -0500
X-Mailer: PerfectMail

>> Testing the SMTP connection.
>> .
<< 250 2.0.0 qAJHSKTL017642 Message accepted for delivery
[-] Closed connection
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