Here is the bounce message
5.1.0 - Unknown address error 530-"Recipient refused. The sender's domain requires authentication or is not a valid user."
The attached email that bounced is from me, to me.
Here are some exerts from the SMPT log.
11:13:32 -> 208.90.89.33 -> Success: Action=[Received Hello], Details=[Host=po033.quotit.com]
Fri, 27 Sep 2013 11:13:32 -> 208.90.89.33 -> Success: Action=[SPAM Detection Triggered], Details=[SPAM detected by Sender Domain Check.]
Fri, 27 Sep 2013 11:13:32 -> 208.90.89.33 -> Success: Action=[Received Sender], Details=[Michael@insureyoutoo.com]