What do the flags in a Maildir message filename mean?

Question

I'm cleaning up some old Maildir folders, and finding messages with names like:

1095812260.M625118P61205V0300FF04I002DC537_0.redoak.cise.ufl.edu,S=2576:2,ST

They don't show up in my IMAP client, so I presume there's some semaphore indicating the message already got moved somewhere else. Is that the case, and can the files be deleted without remorse?

Answer 1

I'm assuming this file is from a Maildir folder?

The 'M' is just part of the unique filename and has nothing to do with the fact that the mail doesn't show up in mail clients.

The 'T' at the end of the filename, after the ':' sign, however tells the IMAP server that this message is Trashed.

See http://cr.yp.to/proto/maildir.html

Answer 2

IMAP, is a protocol for communicating to a message storage, the actual storage is standardised in other ways. The filename looks like a Maildir filename where I think does not put any meaning into the first part of the filename, but you have to check with your software manual.