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
