Add a MDBadQueueReason: column to the Bad Queue contents list.
There is already a MDBadQueueReason: header in bad messages which indicates why they are considered bad.
Adding this to the stats view would make it easier to spot a persistent problem with certain mail routes, etc.
MDaemon 13.5.0 was updated to show the MDBadQueueReason header when viewing the messages from within the GUI.
As far as I'm aware the only way for messages to be placed in the Bad queue without getting the header added is by a content filter rule. If you are seeing messages added to the Bad queue by something other than the content filter that are not getting the header added, please contact technical support so that we may investigate the issue and fix it.
Erik Likvarn commented
The thing is that not all messages that end up in the bad queue have that field in the header. Sometimes it is unnecessarily difficult to figure out what is so "Bad" about a message.
All messages that end up in the Bad message queue should have the header field added AND have that reason displayed in the GUI.