Spam filtering with backup mx servers
Question asked by Robbie Wright - 11/18/2016 at 8:09 AM
We're playing around with Cyren on our primary mail server and it seems to be working pretty well, and catching most of the other 3% of mail SM doesn't think it'll catch. We have a backup mx server in a different data center that was previously setup to do its own spam scanning and pass the score to the main server. However, since we're licensing Cyren (well, currently in a trial) on our main server and I'd rather not pay for it twice, I'd like the backup MX to no long do anything with spam, pass everything to the primary server, and have it (and Cyren) do the spam scanning. How would we go about setting that up?

We currently have the spam settings config'd on the backup mx to "take no action" and the IP address of the backup mx is added in the bypass gateway section of the primary server. The backup MX is config'd to do user verification through web services against the primary server currently.

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Linda Pagillo Replied
Hi Robbie. I think the best thing to do in this case would be to turn the backup MX server into a gateway. All mail that is destined for your primary server that's coming via your backup MX should just be passed along with no action taken on spam. As your primary server needs to scan all messages from your backup MX, you cannot whitelist the backup MX server. You need to treat it like any other external server. The one problem that you may face is that your primary mail server may see all messages coming from the backup MX IP address, which defeats the purpose of using RBLs. If this is the case, something like Declude can help because it can be configured to hop over your backup MX IP and see the original sending IP. Declude is free of charge and you can get it here: http://mailsbestfriend.com/downloads.Please let me know if you have any questions. Thanks.
Linda Pagillo
Mail's Best Friend
Email: linda.pagillo@mailsbestfriend.com
Web: www.mailsbestfriend.com
Authorized SmarterTools Reseller
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kevind Replied
Robbie, good question and certainly good timing with the deluge of emails being sent out due to Black Friday Cyber Monday, etc. See this post from last year (and vote for it) to improve SmarterMail's gateway integration.
It fixes the problem you brought up about licensing 2 copies of Cyren. Most gateway servers use the free copy of SM and I don't think you can even purchase Cyren for that version.

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