Exchange 5.5 event errors.

I’m getting an Event 2018 in me Exchange log when I send from hotmail to it. Transfer Out of Gateway to the Private is in the details with a 0x80004002. At one time we had hotmail as blocked domain in the IMS but have since removed it. I have done this with other domains and not had a problem. Normaly blocked domains give an IMC error in the event log. The only other info I can find on this says it may be related to AV software. I’ve already seen the MS KB on this and we are on the latestSP already.