Outbound Messages - Inconsistent delivery

[MichaelBurton]

I can't get outbound messages to deliver consistently.  I keep getting the message: org.xml.sax.SAXParseException: Content is not allowed in prolog.  If I click retry in the Oubound Message delivery monitoring screen, the messages go through but we send hundreds of messages a day.  Anyone have an idea how to avoid that failure?  If I don't hit retry, the messages will continue to attempt and fail.  

[SimonF]

You really need to see what your endpoint is returning in the error case, have you tried using a network capture tool like wireshark to see the actual response in these cases. Does your endpoint correctly handle the case when the server sends multiple notitications in a single soap message.?