hope someone can shed some light on this as it is driving me nuts.
I have a single user in our exchange 2010 organization that is unable to receive mail from a single external user.
I have had the user send me a transcript of her NDR and she is receiving
<tt><<< 554 5.1.0 Sender denied</tt>
<tt>554 5.0.0 Service unavailable</tt>
<tt>I have checked all of the filters on the transport server and can't find a reason why she should be being bounced. </tt>
<tt>I have even added her to bypassed senders in the contentfilter config in the hopes it might be something odd with anti-spam, but that does not appear to be the case. </tt>
<tt>Whilst the user sending the mail is from the aol.com domain, we do not appear to be experiencing this issue with other users sending from aol.com</tt>
<tt>I'm stumped.... Any clues please??</tt>