Type says what a letter is; status says where it has got to; priority says how much it matters. Together they are what the register can be filtered and reported on.
This topic includes:
Types
Types are set per project so they match how your contract talks. Common ones are letters, instructions, notices, transmittals and early warnings. Choosing the type at the point of writing costs a second; classifying two hundred threads afterwards costs a day.
Status
A thread is open while it is live and closed once it is finished with. Closing is not the same as replying: a thread stays open while an answer is still owed, which is what makes the open list the list worth reading before a meeting.
Priority and due dates
Priority — low, normal, high — and a due date together answer "what is late". Set a due date whenever the letter asks for something by a date; leave it empty when it does not, so the overdue list stays meaningful.
Deleted threads
Deleted correspondence is hidden rather than destroyed: toggle deleted threads back into the list to see them, and restore one that should not have gone. As with everything else on the project, prefer closing to deleting — the record of a letter that came to nothing is still a record.