> Show me ONE major MTA which allows you to configure an expiration
> for an ACL entry.Any MTA which supports using an sql db as its backend. Postfix is a
fine example.You just define the table and the query to either have an until column,
or have a column with the timestamp of when the entry was added and have
the query ignore rows which are older than some given time.And with postfix, using its sql proxy capability, using a sql backend is
fully performant.
So, you agree, MTA's do not implement this functionality. It's obviously
possible to make it happen through shell scripting, database tricks, etc.,
but the point was that if this was commonly desired, then MTA's would be
supporting it directly. It isn't commonly desired, most people just block
"forever."
It never ceases to amaze me how technical people so often easily miss the
point. 
... JG