Robert,
You will have to modify the files slightly that are sitting in the OutboundMailQueue. Here are the steps:
- Open $INSTALL_DIR\OutboundMailQueue folder
- Open any file sitting there in Notepad
- Search for X-SMCustomAuth .
- The goal is to remove this header from the email that are sitting in your OutboundQueue. The quickest way is to use a utility that can do search/replace inside files and replace X-SMCustomAuth with some garbage value. For example X-SMCustomXXXAuth
The actual problem is occurring when Xeams is trying to use the Smart Host even for incoming messages.