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We allow users to forward their e-mail to external addresses.

From time to time, our mail gateway appliances' anti-spam engine computes a large spam campaign targeted to our users as a false-negative. These messages, in turn, get forwarded to the external e-mail addresses (per the user's configuration). Those external e-mail providers then blacklist us.

I'd like suggestions on how to prevent this while still allowing users to forward messages.

Thank you in advance.

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3  
Don't send spam. Don't allow others to use or abuse or trick your system into sending spam. If you fail to do that then others can and will block you. It's not really very difficult. I think you're talking about backscatter, which is a well known problem by now and if your antispam system can't cope with it then you should consider replacing it with one that works properly. –  RobM Jul 14 '11 at 14:40
    
You misunderstood my issue (I probably did not explain it well enough). Users are receiving spam. Since we have mail forwarding, the spam is being forwarded to external mail servers. Because of that, we are being blacklisted. –  Belmin Fernandez Jul 14 '11 at 14:45
    
I am NOT talking about backscatter. Tried to clarify the language a bit. Let me know if it's clear enough. –  Belmin Fernandez Jul 14 '11 at 14:49
    
For fellow SF'ers who are upvoting Mr. Moir's comment: I believe I did not explain my question well enough. I have expanded on that now. If anyone has any questions, please feel free to comment! –  Belmin Fernandez Jul 14 '11 at 15:05
    
Well now that you've clarified your original question it makes more sense but it comes down to this being an inherent problem with allowing people to forward email from your system that might include spam. There's not a lot you can do besides stopping the forwarding service; no matter what you do, inadvertently forwarded spam will look like spam, and other email providers will block you for sending what appears to be spam. –  RobM Jul 14 '11 at 16:54

1 Answer 1

up vote 4 down vote accepted

The receiving mail system cannot tell the difference between forwarded spam and real spam. If you forward email, you always have the huge risk of blacklist unless you control the receiving mail system as well.

This happens often with web hosting accounts forwarding the email for a domain to Gmail, Yahoo, Hotmail, Aol, etc. You can either constantly fight the blacklist, or encourage users to take advantage of the POP access of some accounts. Gmail has an easy feature to automatically download email from any POP inbox into your account.

Anyone with a desktop or mobile email client can be downloading the email directly instead of forwarding it. Make sure users know the risks of forwarding, and that you're doing everything you can to keep the system out of blacklists... but that it will very likely continue to happen as long as they're forwarding and getting spam.

If users are forwarding so they have a single web-based inbox and do not currently use a service allowing POP integration, they do have the option of switching to Gmail and using delegation for both of their addresses.

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Thank you. That is a good suggestion. I will bring that up with management and see what they think. –  Belmin Fernandez Jul 14 '11 at 15:02

protected by Michael Hampton Nov 30 '12 at 3:36

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