Unfortunately, this little MS-behaviour is very likely to be the "last
straw" that gets our greylisting turned off here.
Despite my logs that prove that greylisting has removed over 95% of
incoming spam before spamassassin has to deal with it, the fact that
some legitimate mail is lost or overly delayed has been deemed
unacceptable to the corporate masters. The people inconvenienced by
this pay more in taxes than I make in a year so they need to be kept
happy. And the mail that is often missed is quite often something
time-sensitive. It really is a shame. Greylisting has made such a huge
difference in the spam-volume here. We receive about 10 complaints per
week about either mail that never came in or mail that came in too late
to act on. These missing emails have sometimes cost us tens of
thousands of dollars in lost profits. So that makes the tens of
thousands of blocked emails per day seem a lot less significant. I have
whitelisted source IPs where possible but there is always some new
complaint right around the corner. They appreciate the reduction in
spam that gets through but they are the first to complain if mail is
delayed or if they don't get something. In the financial trading
sector, you would be shocked at the number of small, one-man analyst
companies operate from home and send out mail to subscribers from
dynamic IP addresses. Couple that with lots of non-standard mailers and
it's a wonder any of their mail makes it past a decent SMTP
sanity-checker...
