Open connection

Command:

[hanez@phantom ~]$ telnet mail.domain.tld 25

You should normally receive something like this:

Trying 000.000.000.000...
Connected to mail.domain.tld.
Escape character is '^]'.
220 mail.domain.tld ESMTP

Say hello

Command:

HELO local.domain

Answer (normally):

250 mail.domain.tld

Set the sender

Command:

MAIL FROM: user@domain.tld

Answer (normally):

250 OK

Set the recipient

Command:

RCPT TO: user@domain.tld

Answer (normally):

250 OK

Compose the message

Command:

DATA

Answer (normally):

354 go ahead

Start writing content in the message

Insert data:

Subject: "Hello World!"

Hello World,

what's up?

Sending the message

Enter a new line after the last word you have written. Add only a . (dot) to this line. Hit enter.

.

If everything was ok you should receive a message like this and the mail should be sent:

250 ok 1090795155 qp 29731

That's it.