Why do I get Protocol Errors when emailing AOL users?

[khrush2003]

I am unable to send emails to contacts with AOL accounts.
I get an error message from my Exchange 5.5 server.
A mail message was not sent due to a protocol error.

554 TRANSACTION FAILED
The message that caused this notification was:


To: <*****@aol.com>
From: <****@****>
Subject: Test

I have rDNS set up
Any help would be gratefully appreciated

 

[Adam Bailey]

I am unable to send emails to contacts with AOL accounts.
I get an error message from my Exchange 5.5 server.
A mail message was not sent due to a protocol error.

554 TRANSACTION FAILED

http://members.aol.com/adamkb/aol/mailfaq/#receiving