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I need to be able to restrict the amount of bandwidth used by SMTP port 25. Basically, we have a routine in our server software that will send out bulk faxes, not much data per fax but a lot of different faxes to send. This is done over SMTP to a fax relay. However, when a particularly large amount goes through, we notice a decrease in the performance on the server and the internet connection in general.

Does anybody know of any software that would allow me to set up restrictions on this process?


SMTP server is VPOP3 running locally on Windows Server 2000. The OS on the live servers are Windows Server 2000 and Windows Server 2008. The relay is external ( We want to restrict everybody sending faxes. Other emails can be restricted also.

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What OS? What SMTP server do you use? Internal (LAN) or external messages? Is the relay on the same network? Or an external provider? Do you need to restrict users or PCs? Just faxes? Or other emails in general? – saschabeaumont May 13 '09 at 12:41
up vote 1 down vote accepted

VPOP3 can limit its own bandwidth usage. See this knowledgebase article.

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Thanks for the help, This seems to be working a treat. – Sangai May 14 '09 at 8:44

One solution would be to set up an intermediate smtp server that only accepts 1 connection at a time, which then forwards into your main smtp relay.

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note: I have set up 2 smtp servers on the same box in the past - just use different ports. – Brent May 13 '09 at 13:01

You can also install a firewall/proxy that does traffic shaping if you don't have one already. IPCop comes to mind, although it doesn't have very fine-grained control over traffic shaping.

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