#295 UIDVALIDITY is always 1

[Jos]

UIDVALIDITY should change when the contents of a folder changes but DavMail always returns '1'.

"Any change of unique identifiers between sessions MUST be detectable using the UIDVALIDITY mechanism discussed below."

https://tools.ietf.org/html/rfc3501#section-2.3.1.1

[Mickael Guessant]

Well, IMAP uids retrieved from Exchange do not change between sessions, so the uidvalidity does not have to change => the easiest implementation is to always return 1.

Note that on Exchange message uid does change whenever you touch the message => each touched message will appear as a new message.

[Jos]

My interpretation is different. UIDVALIDITY should also show these changes between sessions. As long as the UIDVALIDITY and UID are the same the message should be exactly the same, only the flags may change. The point of this is that messages can be cached. If DavMail keeps a running set of UIDs and only hands them out to new or changed messages, then it is fine to not change UIDVALIDITY. That would mean that either Exchange tracks this correctly or that DavMail keeps a state for each account.

[Mickael Guessant]

Well, that's the case: Exchange tracks changes on messages and changes uid on any change on the message, thus you will never have a message content change without a new uid => uidvalidity is useless with Exchange