bounce prevention

[tminchin_ironport]

has anyone used the newish "unwanted bounce" prevention that is in 4.7?

we have a few users who seem to get forged a lot and this looks like a useful feature. However, I'm keen to know if re-writing the envelope sender has caused anyone grief in the wild?

[shannon.hagan]

It is based on Bounce Address Tag Validation which you can find on the ietf website ( http://tools.ietf.org/html/draft-levine-mass-batv )

The one thing you need to consider is whether your users send mail out to places without going through you. If they do, you aren't tagging the message on the way out.

[tminchin_ironport]

thanks for that link. They have a set of problem areas in the RFC:

1) greylisting - avoidable if the tag is constant
2) mailiing lists - lists that use MAIL FROM to determine access to lists will not work (either reject all messages or pass them to a moderator)
3) challenge-response systems - every message will generate a C-R
4) sorting and duplicate detection - including whitelists which use MAIL FROM

we might wait for a few braver people to try it out (and we can look at the arrow wounds)