On Mon, 12 Nov 2007, Douglas Otis wrote:
When the SMTP client's reputation is unknown, an SMTP server is unlikely
to Perm Error at the EHLO. Temp Errors at this point might be used to
discern whether the SMTP client keeps state, as with greylisting. Temp
errors might also be used to delay acceptance when a spam campaign is
detected as being active at an SMTP client handling messages from both
good and bad actors. TBR provides a safe alternative to greylisting and
I agree that it is a worthwhile goal to reduce the interop problems of
greylisting, and I agree that delaying email from unknown sources might
give blacklists time to make a decision about the source.
However, I believe that in doubtful cases it's better to apply AI to the
complete message data than to attempt to analyse some abbreviated
notification. In most cases MTAs have enough capacity to do this: at the
moment (according to my stats) doubtful cases are about 30% of the email
that gets past blacklists.
I think it would be more useful for you to try to fix greylisting than to
redesign IM2000 yet again.
f.a.n.finch <dot(_at_)dotat(_dot_)at> http://dotat.at/
DOVER WIGHT: WEST 5 OR 6 VEERING NORTH OR NORTHWEST 5 TO 7, PERHAPS GALE 8
LATER. SLIGHT OR MODERATE, BECOMING ROUGH FOR A TIME. SQUALLY SHOWERS. GOOD.