In 2008, you should have queueing. DB MAil uses Service Broker under the covers, so I wouldn't worry about that.

http://msdn.microsoft.com/en-us/library/ms190307.aspx

I do think Sean could be right that you have a problem with your @message. I would say build a table, use a column for each part of @message, adn insert there. Then look at that to debug.

Be careful with this type of auditing. You may end up with very, very large amounts of data and emails.