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Netmail Secure (all versions)


This article describes how to telnet to the Netmail Secure server on Port 25 (the default SMTP port) to test and troubleshoot SMTP communication problems. This procedure quickly tests whether the Netmail Secure server can receive mail messages and queue them for delivery. Once the message is queued, it can be determined if it gets stuck in the queue (a.k.a. the spool) or gets delivered to the recipient's mailbox. Mail routing is also tested.


1) Using an SSH client such as PuTTY, connect to the Netmail Secure server and log in. Once logged in, gain root priviledges by invoking the sudo su command.

2) Establish a TCP connection to the SMTP port by invoking the following command: telnet localhost 25 

(this can also be used to test communication between two servers)

3) If the server is listening, it should reply as follows:


Connected to localhost.

Escape character is '^]'.

220 linux-sec51 Netmail Secure Extreme Email Engine ESMTP ready 5.2.2.release


4) The 220 response indicates that the server is listening. Initiate SMTP communication by typing the following command (using the sending server's hostname):


The Mail Transfer Agent will respond with a list of features it supports: Pleased to meet you
250 SIZE


5) Before generating the body of the test message, type the following command to tell the receiving SMTP server who the message is from. For the purpose of the test, this can be any SMTP address such as

mail from:<>

The SMTP server should respond will a return code that starts with a '2' (return codes that start with a '2' are good news):

250 Sender OK


6) Once the sender is acknowledged, tell the receiving SMTP server who the message recipient is (use a valid SMTP address): 

rcpt to:<>

The receiving server should return the following command:

250 Recipient OK


7) Enter the following command to the let the receiving SMTP server know that mail data is ready to be sent:


The receiving server will acknowledge (meaning the message can now be sent), and the response will indicate that the input should end with a dot on an empty line (followed by pressing the enter key):

354 Send message, end with <CRLF>.<CRLF>


8) Next, type the body of the mail message (and note that there should be a period on the line following the message end followed by pressing the enter key):

Hi Example,

This is a test message.

9) The following response indicates that the message was received and queued under a queue ID:

250 OK


10) The last command step is to close the connection with the following command:


The following response will be returned from the SMTP server:

221 closing connection Live long and prosper


11) The final step is to access the Netmail Administration Console to verify that the test message was received.

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