[MlMt] IMAP problem UIDVALIDITY

[Benny Kjær Nielsen]

On 22 Feb 2017, at 19:04, Alain Israel wrote:

> When I arrived this morning, I got the following message (below), and 
> all my mailboxes were offline. I pressed « always resynchronize » 
> and everything resumed, albeit quite slowly. Is this diagnostic of 
> something specific (it is the first time it occurs in about a year)?

The UIDVALIDITY value for an IMAP mailbox is what an email client uses 
to determine if a mailbox is still the same mailbox. The name is not 
sufficient, because another email client might have deleted a mailbox 
and then created a new one with the same name. This could lead to an 
incorrect mapping between local emails and server emails. Therefore, a 
changed UIDVALIDITY value for a mailbox signals that the email client 
should forget everything about the mailbox and re-synchronize it. It's 
the only safe option.

I cannot tell you why this happened, but if it happens on a regular 
basis then we can debug to make sure that MailMate does not behave 
incorrectly (I doubt it since if it did then it would likely happen very 
often).

Some IMAP servers are pretty buggy regarding the UIDVALIDITY value, but 
there's not much MailMate can do about that.

> Resynchronize - Always Resynchronize - Retry

The “Always Resynchronize” button was implemented to help out with 
such buggy servers. I won't recommend using it in general and the 
setting is forgotten as soon as MailMate is relaunched.

(One could imagine a server which deletes certain empty IMAP mailboxes. 
This could trigger new UIDVALIDITY values on a regular basis, but in 
this case it's not really doing any harm.)

-- 
Benny