[Spacecowboy2005]

Right, I've spent hours reading posts and getting no where with this!

We're running Exchange 2003 on a Windows Server 2003 box. All mail that comes in to valid users is forwarded to another address on another domain.

For example:

me@123.com forwards to me@123-abc.com

This had been working fine for almost a year, until a few weeks ago.
Now the problem is that recently these messages just sit in queues, sometimes the mail is gradually released but never the whole queue.

There are also several queues forming with NDR reports to random domains.

Error messages displayed are;
"The connection was dropped due to an SMTP protocol event sink."
or
"Unable to bind to the destination server in DNS"

I've read that this can be related to External DNS so have added and External DNS to the Deafult SMTP Virtual Server. This hasn't helped.

I also was lead to belive this was a RNDR attack as per http://support.microsoft.com/kb/909005 but i have Recipent filtering enabled and this is still occuring

I'm completly stumped as to what is happening, if there is an exchange guru that could help me out i'd be very very greatful

Thanks