SMTP conversation - Troubleshooting mail servers

The basic SMTP commands are: HELO or EHLO , MAIL FROM: , RCPT TO: , DATA , and QUIT.

Date: , From: , Subject: ,and To: may be used within DATA.

The best way to troubleshoot mail servers is using telnet or netcat.

Here is a simple SMTP conversation.
g:~$ netcat archimedes.ipduh.com 25
220 archimedes.ipduh.com ESMTP srv
ehlo gov.us
250-archimedes.ipduh.com
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250 DSN
mail from: < president@gov.us >
250 2.1.0 Ok
rcpt to: < n@arc.ipduh.com >
250 2.1.5 Ok
data
354 End data with .
To:< n >
From:< el presidente >
Subject: What up n?

I am not going to be able to able to reform the health system.
No dough, no doc.                  
.
250 2.0.0 Ok: queued as E69D97B299E
quit
221 2.0.0 Bye
g:~$ 


The best reference on SMTP commands is RFC5321

SMTP conversation - Troubleshooting mail servers