Re: [exim] Greylisting - Chnging IPs

Dean Brooks wrote:
> On Sat, May 10, 2008 at 12:16:03AM +0200, Heiko Schlittermann wrote:
>> Hello David,
>>
>> David Woodhouse <dwmw2@???> (Do 08 Mai 2008 14:10:21 CEST):
>>> It means that you shouldn't include the originating IP address as one of
>>> the criteria for matching emails. I use {sender,recipients,message-id}.
>> But this means that you're greylisting in your DATA acl (to get the
>> message id). Didn't you experience problems with returning a 4xx there?
>> I'm talking about serious operated MTAs being choked on 4xx after
>> sending the final dot. (Despite the fact that some RFC allows 4xx at
>> this point.)
>
> What kind of problems would you expect to see?
>

Some versions of MS exchange do strange things when receiving a 4xx
error at the end of data. They just hide the message from the queue (you
cannot even search for it, you will not find it) and the message is
never retried. But if the server is rebooted (or any other thing
restarting the MTA part) the message comes back into the queue. This is
not often a problem as MS servers tend to be rebooted each week. The
version of exchange doing this is 2003 but not all the times, it seems
this is due to a combination of patch level in the OS and patch level in
exchange itself. It is not trivial to reproduce but I have seen it
happen more than once.