hey everyone...i'm trying to configure a simple ACL to block smtp traffic from leaving my LAN -- basically prevent internal users from setting up internet email accounts in their email clients and sending through that smtp server. i want my Exchange server only to send smtp traffic. here's what i have:
access-list 102 extended permit tcp host 10.10.1.29 eq smtp any eq smtp <===10.10.1.29 is Exchange
access-list 102 extended deny tcp any eq smtp any eq smtp
access-list 102 extended permit ip any any
access-group 102 in interface inside
after i apply this ACL to the ASA, i am still able to send from my internet email address setup in Outlook using my "foreign" smtp server. what am i missing? Thanks very much.
many email-clients send mail through port tcp/587 which is used for SMTP with authentication. You need to block that as well.
And your ACL is wrong. It has to be that:
access-list 102 extended permit tcp host 10.10.1.29 any eq smtp access-list 102 extended deny tcp any any eq smtp access-list 102 extended deny tcp any any eq 587 access-list 102 extended permit ip any any
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