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Abstract

An email message requires some amount of processing when it is redistributed to a mailing list. At the very least, the envelope must be rewritten to redirect bounces directly to the list administrator. While the message is being processed, the list administrator might take advantage of the opportunity to munge some of the message headers.

Some forms of header munging are helpful, such as special loop-detection headers. Others are questionable. Most are ill-advised or dangerous. Many list adminstrators want to add a Reply-To header that points back to the list. This transformation also is one of the most ill-advised.

Some administrators claim that Reply-To munging makes it easier for users to respond to the entire list, and helps encourage list traffic. These benefits are fallacious. Moreover, Reply-To can have harmful -- even dangerous -- effects. If you think Reply-To munging is a good idea, I hope I can change your mind.