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We have and ISP with adsl , broadband etc subscribers (average 10000 online users with 1M of Bandwidth . average ) . Some users infected by spammer viruses which makes our ip address spaces blacklisted in RBLs . I am looking for a transparent solution without need any change at client side.

average mail traffic is about 3Mb .

Omid Kosari
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1 Answers1

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Block outgoing port 25 at your egress, except for traffic to/from your own mailserver, and business customers who request it to be unblocked. Then require customers to relay all their mail through it.

Michael Hampton
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  • Sorry but that's not the solution . as i said i am looking for transparent solution without need to change client side – Omid Kosari Aug 04 '13 at 09:17
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    That _is_ the solution, sorry. – Michael Hampton Aug 04 '13 at 09:20
  • What about something like http://sourceforge.net/projects/assp/ ? – Omid Kosari Aug 04 '13 at 09:25
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    None of your customers have legitimate port 25 traffic **AT ALL** unless they're businesses running an in-house mail server. – Michael Hampton Aug 04 '13 at 09:26
  • By the definition of transparent, there can exist no transparent solution that stops your users from sending spam. However, blocking port 25 except where the user advises you they wish to run a mailserver, like all reputable ISPs do, requires no client-side changes because you can do it at the gateway of demarcation. There exists absolutely no other correct solution to this problem. – Falcon Momot Aug 04 '13 at 09:42