Hi all

During the last few days spent tracking strange problems with exchange servers from different companies.

From my actual point of view exchange server seam to have troubles with tempfail messages. They notice a 4xx error, tryes again a few times and then occasionaly returns the email to the sender with following message:

"Sie sind nicht berechtigt, Nachrichten an diesen Empfänger zu senden. Wenden Sie sich an den Systemadministrator." 550 5.7.1 <lucciola@*>... Relaying denied>

This Relaying denied definitely is not from the server receiving the email. There I can only find tempfails. I also have seen other messages than relaying denied there which made even less sense.

This happened a few times with graylists tempfails and also happens with a customer sending quite a lot of mails from his exchange and running into sendmails reject=452 4.3.2 Too many open connections. limit.

Have other seen this behaviour of exchange servers and know how to prevent it?

The strage thing is this only seams happens occasionaly. It can be that the customer sends a mail to hundreds of recipients, causes many tempfails about 'too many open connections' but the emails eventualy get through without problem after a while.

I guess it could be, that exchange mixes up message status from other emails and just sends the wrong error message back to the sender.

Mit freundlichen Grüssen

Benoit Panizzon