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SMTP (Simple Mail Transfer Protocol) is a protocol for servers to send email between one another. Most common mail protocol on the Internet.
Tips and tricks
You can manually contact your SMTP server using telnet to send email. All you need to know is the server's name and the port (usually 25).
Authenticate using telnet
telnet localhost 25 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 duffman.site ESMTP Postfix
Send the SMTP authentication command
AUTH LOGIN 334 VXNlcm5hbWU6
Send the username base-64-encrypted (dummy in this case).
ZHVtbXk= 334 UGFzc3dvcmQ6
Send the password base64 encrypted
cGFzc3dvcmQ= 235 2.7.0 Authentication successful
Send a mail using telnet
So let's telnet in:
telnet mail.somehost.com 25
You should now be greeted by some text that looks like:
Trying 22.214.171.124... Connected to mail.somehost.com Escape character is '^]' 220 sbh14.somehost.com ESMTP server ready Wed, 15 Mar 2004 02:32:40 +0100
Now to start sending your mail you write:
HELO somehost.com MAIL FROM:<email@example.com>
Note: You can specify any address as the sender, because there is no sender verification
RCPT TO:<firstname.lastname@example.org> DATA Subject:Hello World! From:Elvis Presley <email@example.com> Hi you at mailaddress. This is a mail sent by telnetting to an smtp server. You can write as much as you want here. When you are finished enter a . as the only character on a new line. Yours, Elvis .
To quit just write quit