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linktree Topic: Firewall rule to block outbound SMTP
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Topic: Firewall rule to block outbound SMTP  (Read 2439 times)
« on: August 21, 2008, 03:08:09 »
bbanis2k *
Posts: 1
Greetings,

I have a rule on my LAN to allow 192.168.1.32 SMTP ---> Any SMTP 

Then I have a rule to block LAN SMTP ---> Any SMTP 

Then I have a rule to allow LAN any * ---> Any *

The problem I have is that any workstation can send outbound mail, and not just my Exchange server.  It is as though they all default to the bottom rule of allowing all traffic.  Any help would be great!!!
« Reply #1 on: August 21, 2008, 13:57:50 »
Manuel Kasper
Administrator 		*****
Posts: 364
On your first and second rules, the source port should be "any" (only the destination port should be set to SMTP/25), as the source port is going to be randomly chosen by the client.
« Reply #2 on: August 21, 2008, 14:50:21 »
markb ****
Posts: 331
Manuel is spot on.  while not an answer to your original question, I would suggest that you not leave a pass any to any rule, but rather be specific to what traffic you want to allow out, such as, ntp, dns, http, https, ftp etc. Then end with a block all rule.
This is just a suggestion to give you a more secure network.

Regards.
 
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