Diagnose .HELD Files

From MsgServerDocWiki

How can I diagnose and clean up .HELD files?

If the MTA detects that messages are bouncing between servers or channels, delivery is halted and the messages are stored in a file with the suffix .HELD in the msg-srv-base/data/queue/channel directory. Typically, a message loop occurs because each server or channel thinks the other is responsible for delivery of the message.

See the following blog entry for more information: http://blogs.sun.com/factotum/entry/messaging_server_diagnosing_and_cleaning.