Start off by opening a command prompt or terminal shell
then type:     telnet mail.domain.ext 25
You should receive a reply like saying “220″ and the service is ready followed by the date/time. This depends on how your email server is configured.
Example:
220 mail.domain.ext ESMTP Service ready at date+time+gmtoffset? (or somehting similiar)

Now that you are connected you will then need to delcare where you are sending the email from:
HELO domain.name – dont worry too much about your local domain name although you really should use your exact fully qualified domain name as seen by the outside world the mail server has no choice but to take your word for it as of RFC822-RFC1123.
This should give you:
250 mail.domain.ext Hello local.domain.name [loc.al.i.p], Hello

Now give the “from” email address:
MAIL FROM: mail@domain.ext
Results:
250 2.1.0 mail@domain.ext… Sender ok

Now give the recipients address:
RCPT TO: mail@otherdomain.ext
Results:
250 2.1.0 mail@otherdomain.ext… Recipient ok

For adding a subject to the test email issue the “Subject:” command followed by your subject

To start composing the message issue the command DATA
You should recieve a message stating that you can start typing message.
To tell the mail server that you have completed the message enter a single “.” on a line on it’s own.
The mail server should reply with message accepted for delivery or queued mail for delivery.

You can close the connection by issuing the QUIT command.
The mailserver should reply with something like:221 2.0.0 mail.domain.ext closing connection
Connection closed by foreign host.