I'm facing a problem with a slow (custom) BizTalk adapter.

Every night, an application sends more than 10'000 messages to a MSMQ within a few minutes.
Unfortunately it takes hours for BizTalk to process them.

I do not have any orchestration, just route the messages to several parties.
For one party we had to develop a custom adapter, but this adapter/interface is very slow.
So I think BizTalk automatically throttles down the whole application and only reads as many messages from the queue that it can send over this slow adapter.

Therefore it takes hours till the MSMQ is empty.

If I stop this slow adapter and e.g. only enable a File Adapter that writes to the local file system, it takes a few seconds to process the thousands of messages from the MSMQ.

Is it possible to tweak BizTalk to process the incoming messages faster and just throttle the outgoing messages for this send port? It's unfortunate that all other parties have to wait for the messages because of one slow party.

Thank you for any advice!

Best regards
Michael