Unwanted Mail Relay can’t track it down

A couple of weeks ago, I started receiving messages from my system stating the following: (incoming mail)
The following recipients did not receive the attached mail. Reasons are listed with each recipient:

mailrelay%ort-r01.mx.aol.com@exchangesrvr.domain.wa.gov
MSEXCH:IMS:WA.GOV:domain:exchangesrvr 0 (000C05A6) Unknown Recipient

The message that caused this notification was:

I always receive with this one an outgoing messagestating:

A mail message could not be sent because the following host is unknown:

xxx.xxx.xxx.xxx
The message that caused this notification was:

To: ;
From:
Subject:

I changed some of the info for security purposes, but cannot track where this is coming from and how to get rid of it. Any ideas out there?