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On the mail servers I set up in our company, I use several blacklists in postfix. These really help take care of the spam we get send our way.

But every once in a while one of our (potential) customers can't send us mails because they are on such a blacklist. And it usually isn't a false-positive. They sometimes share mail servers with other companies on a server by some hosting company. Or they send out particularly large amounts of "newsletters".

While this happens rarely, when it happens, it's very hard to deal with. Because obviously the problem is our mail server. As they have no problem sending mail to other people. I usually tell our people that I won't change our perfectly fine config to allow people with messed up email servers (or ethics) to send us mail.

Referring these people to removal request pages of the RBL is pointless either. These are usually people in marketing who have no clue what I'm talking about (and don't care for it either).

But that still leaves me with the problem that we would like to be able to receive mail from them.

How do you handle a situation like that in your company?

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If you're finding the blacklists to be unreliable for your purposes then I have to suggest that you either shouldn't be using them or you should be using different ones. – RobM May 27 '11 at 12:01
up vote 8 down vote accepted
  • Whitelist before you blacklist (manually, automatic, DNS based such as
  • Don't reject mail based on a single blacklist (think about the power you are giving their operators), but use scoring system based on multiple spam characteristics).
  • Keep complaining to them. Try to convince them that they are going to have deliverability problems with a lot more people (Gmail, Hotmail, customers) if they ignore the listing.
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+many, if I could, for the suggestion about scoring. There is NO blacklist that I would recommend using as a bright-line test, as they're all subject to fault. Using them to drive a scored reputation-based system, in the manner of spamassassin, has always worked much better for me. – MadHatter May 27 '11 at 11:45

A white list usually takes precedence over a black list. You also need to be choosy about who you use for a black list...some are more militant than others, or technically sound. If you use someone, who blacklists too easily, you may want to change. There can be a happy medium, so if this is happening to you a lot, either you happen to work in a field with a lot of people, who happen to get blacklisted, or it is possible that your system is not as good as you think. Consider a different, more moderate list.

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We actually use several list together. But over the years we reduced the list to the few that work best for us (except for the case noted in the question). – Oliver Salzburg May 27 '11 at 15:55

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