SMTP Access Rule includes what port(s)?

[smiths@prpa.org]

Hi Everyone,

Does the ASAs access rules for smtp filtering include all smtp ports used or just port 25?

For example, I know Exchange uses 25, 587, 2525, 465 and 475 depending upon server role and function. Port 25 and 587 for server and client connectivity, and 25 or 2525 and 465 on the Mailbox role for accepting internal SMTP connections. So if I wanted to prevent every host from the ability to send mail out of our network; except our Exchange server, would I have to explicidly deny these additional ports or would it be sufficient to deny TCP/SMTP on the ASA?

Steve

[Karsten Iwen]

If you deny tcp/smtp, only port 25 is blocked. The protocol-names that you see in the ACLs are just a placeholder for the typical ports.

If you want to restrict your clients to send mails you need to block all relevant ports. Or even better, follow an restrictive approach where you deny everything and only open the ports that are really needed.


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