What are some things, one should know when setting up an SMTP server, which supports ESMTP protocol. I have disabled relaying, and only enabled TLS authenticated transfers. when I telnet to my server, this is the reply:

250-SIZE 10240000
250 DSN

Should any of these be turned off? should anything else be enabled

  • Have you tried to send a message through telnet to see if you can relay or if SMTP Authentication is required? – AbsoluteƵERØ Jun 10 '13 at 18:56
  • 2
    This looks like a job for the principle of least privilege - disable everything then enable (only) what you need. – James Snell Jun 10 '13 at 18:59

You should disable the VRFY and / or EXPN these commands can expose user information to people probing a system in preparation for an attack.

  • DSN - Delivery Status Notification should be also disabled for the same reasons. – Hugo Jun 17 '13 at 11:10
  • Depending on the objective of the server it might be better to check which options should be configured about the types of notifications that you wish the others to receive. – Hugo Jun 17 '13 at 11:17

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