Our Transactional Dead-letter queue is filling up in MSMQ. I can't find documentation on particular.net that points to why this could be happening.
It looks like every single message that is being processed (successfully) is ending up at the that queue.
What is the reason items are sent to the Transactional Dead Letter queue?
If you open dead letter queue in Computer Management, each message has a reason why it ended up there. It's under "class" column. That should point you where to look. For example one of reasons could be "The time-to-be-received has elapsed.", if message wasn't received within time specified in its "TimeToBeReceived" property.