maxage causes loss of local email

[Janna Martl]

On Fri, Mar 13, 2015 at 11:48:32AM +0100, Nicolas Sebrecht wrote:
> What I care about most:
> - speed for the normal case (most offender: multiple fetches)
> - algo should be as reliable as possible:
>   - working everywhere: IMAP servers have different implementations
>   - all kind of crap that can happen and screw-up the logic (crazy
>     dates, timezones, etc)
>   - prevent failures by avoiding parsing of dates (things like that are
>     usually somewhat haskish and tend to get easily broken)
> 
> FMPOV, you last implementation logic match those pre-requisites and
> properly fix the issue.
> 
> 
> Have fun! ,-)

So I implemented this, tested it, and found that it was still (rarely)
erroneously deleting my mail. Culprit: the IMAP server (gmail)
is actually occasionally assigning UIDs out of order. I tried doing
IMAP by hand, and got the following transcript:

tag fetch 24774 (UID INTERNALDATE)
* 24774 FETCH (UID 45894 INTERNALDATE "15-Feb-2015 15:48:09 +0000")
tag OK Success

tag fetch 24775 (UID INTERNALDATE)
* 24775 FETCH (UID 45895 INTERNALDATE "15-Feb-2015 15:47:41 +0000")
tag OK Success

Am I doing something wrong here, or can we really not trust UIDs to
come in order?

-- J.M.