bug#40089: 27.0.90; nnimap shows empty groups with Cyrus IMAP 3.0.11

[Lars Ingebrigtsen]

Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE> writes:

> Other mail clients (e.g. Thunderbird 68.4.1) show no unexpected
> behaviour, displaying the group contents as expected, and we also got no
> complaints from our users after the server upgrade, which mildly
> suggests an issue on the nnimap side.

[...]

> In the imapd logs, I find many message like
>
> Mar 12 12:04:02 imap cyrus/imaps[29978]: inefficient qresync (1880 > 1503) 
> user.ro.llvm-project

Perhaps these other clients don't use QRESYNC?  Is it possible to switch
on tracing to see whether they do or not?  Because if they don't:

> Prompted by the "inefficient qresync" messages cited above and the fact
> that the previous imapd version didn't support that extension, I tried
> and disabled it in impad.conf (suppress_capabilities: QRESYNC) and
> immediately, everything went back to normal: my nnimap groups show all
> the expected contents and nothing vanishes.

It sounds like that version of Cyrus has a buggy QRESYNC
implementation.  But it's definitely possible that nnimap does something
it doesn't expect QRESYNC-wise...

-- 
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   bloggy blog: http://lars.ingebrigtsen.no