Manually Testing Your Mail Server

By Joshua Erdman
Digital Foundation, inc.

It may be a surprise for you to know that an SMTP session is nothing more than telnet over TCP port 25 instead of port 22.

Because of this you can instantly invoke your own SMTP sessions and send out e-mail without even using a mail client.

The Test

To test we go through 6 steps:

connect
handshake
identify sender
identify recipient
provide message body
end session

All other steps are optional (message priority, subject line, etc).

Connect

To connect just use your cheap telnet program at the run dialog and be sure to specify the SMTP port:

telnet mailserver.com 25

Handshake

The handshake is where you specify your host address. you can really put anything here but if the mail server you are connecting to has spam filtering set up it will reject data that is invalid or does not resolve.

EHLO mail.otherserver.com

Identify Sender

Now when you specify the FROM address, if the receiving mail server is filtering for spam it will expect that the domain listed in your FROM address resolves to the same IP as the domain listed when you provided your mail server name at the handshake.

MAIL FROM:<user@mailserver.com>

Identify Recipient

Most mail servers will accept a message to anyone residing on the mail server. If you try to start a session on an AOL server for example but send a message to a GMAIL address it will be rejected. Mail servers that allow this are known as Open Mail Relays and are usually blacklisted.

RCPT TO:<user@mailserver.com>

Provide Message Body

Here you start by typing the keyword data and then press enter. The Mail Server will instruct you to begin typing the message body and to end by pressing enter, typing a single period and pressing enter again.

DATA
subject:subject goes here
this is my test message
sincerely,
user
.

Notice the period at the end to send the message

End Session

To end the session just type quit.

Article last reviewed: 06/07/2006

Created by: Digital Foundation, inc.

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