Re: reoccuring: Group XY is not uidvalid

[Simon Josefsson <jas@pdc.kth.se>]

Arnd Kohrs <kohrs@ACM.org> writes:

> Can somebody suggest a permanent fix to this problem?  What is
> uidvalid-ness?  How do groups become uid-in-valid ?

A uidvalidity is a number attached to all mailboxes, when it changes
the IMAP client must discard all cached information about the
mailbox. This is primarily used for disconnected IMAP clients which
"cache" lots of stuff.

It's also used to make sure a client doesn't send flag updates (say;
remove article 42) to a mailbox when the mailbox has changed and
article 42 is no longer the article 42 the client believe it is.

Right now nnimap simply complains if uidvalidity on a mailbox changes,
since it can't really do much else -- all flags are kept by Gnus and
there is no official API for backends to request updates in Gnus.

A working long-term solution is to introduce the uidvalidity concept
in Gnus (Gnus Agent) and this is on top of my todo list.