You can usually determine what mail transfer agent software is running on an email server by using Telnet to connect to the mail server on the Simple Mail Transfer Protocol (SMTP) port, port 25. E.g., in the example below Postfix is handling email on the system.
# telnet 127.0.0.1 25 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. 220 jinn.localdomain ESMTP Postfix quit 221 2.0.0 Bye Connection closed by foreign host. #
You can enter SMTP commands that other email servers would issue to send an email to a local user on the system as shown below:
# telnet 127.0.0.1 25 Trying 127.0.0.1... Connected to 127.0.0.1. Escape character is '^]'. 220 jinn.localdomain ESMTP Postfix ehlo Me 250-jinn.localdomain 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-ENHANCEDSTATUSCODES 250-8BITMIME 250 DSN mail from: tester@example.com 250 2.1.0 Ok rcpt to: joe 250 2.1.5 Ok data 354 End data with <CR><LF>.<CR><LF> From: tester22@example.com To: joe@example.com Subject: Just a test This is only a test. . 250 2.0.0 Ok: queued as B27928276DA1 quit 221 2.0.0 Bye Connection closed by foreign host. $
[ More Info ]
