Better Living Through Thinking

Greylisting Cautions

Wed, 09 Jun 2004

It is worth noting that the greylisting might not be suitable for all applications. For example, the other day, someone complained that people who were trying to email him were getting bounces (the 4xx temporary errors). This means that if the sender is sending directly to the MTA from their MUA (where would this occur? If users are on the same server, for example), they (the person) will get the temporary failure message. They may not retry (humans are not RFC compliant and almost never read the error messages they receive).

The trick, I suppose, would be to make sure all your own clients are whitelisted. That would be hard on a large system with possibly roving people. I hear the new version (currently in development) has more ways to whitelist, etc. I'll review that when it goes stable.