Question : Why are we being greylisted?

We run Exchange Server 2003 with Xwall Version 3.31.  Lately, many senders who have been sending to us for years are being greylisted.  I know that there can be many reasons for someone being greylisted, like being added to a greylist, heuristic checking, subject or text blocking, but on many of them,
there is no apparent reason and the messages are not dumped into the message copy folder.

I see things like:  451 4.7.1 message delayed, see http://prolects.puremagic.com/greylisting ; please try again later

and 454 4.5.0 no valid recipients given.

This is becoming a real source of irritation for both the senders and would-be recipients who are all unaware that the emails are not getting thru.

I can go into Xwall Admin when it becomes known that the emails are not getting thru and tell it in the greylisting, heuristing & blocking to let these senders thru, but first you have to know who they are!

Can anyone help?

Answer : Why are we being greylisted?

If you are seeing the messages in the logs then that is fine. The messages will get sent again correctly after a few minutes. Greylisting is a very common antispam measure - I use it with all of my clients as it is still very effective.

Simon.