When I treid to start a project, several SendPorts would not start.  When I tried to start each one manually, some of them were giving this misleading error in the EventLog.

Unable to communicate with MessageBox BizTalkMsgBoxDb on SQL Instance DAL-BIZ-APP01. Error Code: 0x8004d00e. Possible reasons include:
1) The MessageBox is unavailable.
2) The network link from this machine to the MessageBox is down.
3) The DTC Configuration on either this local machine or the machine hosting this MessageBox is incorrect.

We use BizTalk Deployment Framework (BTDF).  I had copied my binding file and updated in Visual Studio.  This is the second or third time that the XML editor of Visual Studio has bit me; it re-arranges the XML in the binding file, and the binding file import is apparently very picky about the layout.  Not sure why it cannot use standard XML conventions.

The moral of the story is to use NotePad++, NotePad or some other safe editor that doesn’t take any liberties with reformatting the XML. I rebuilt my MSI, redeployed, and it worked fine.

What helped me figure it out was this blog:  http://kundankarma.blogspot.com/2012/12/problem-enlisting-send-port.html.
Sure enough I looked at the SendPorts and they had no filters; i.e. the filters had been lost somehow by the editor issue.  Now why it causes the error “unable to communicate with the Messagebox” is entirely a mystery.