Dovecot, JavaMail, UIDs and Message Numbers

[Gabriele Bulfon]

Hi,
new to this list, so a little prelude to my issue with Dovecot.
We have been using JavaMail against Cyrus for ages, and developed Webtop, a huge Java web collaboration application running on them in production in various installations for all this time.
Recently we had to run the same software against Dovecot pre-existing accounts running on Nethesis NethServer solution.
After some time of testing, we started having an intermittent problem, where Dovecot started reindexing when Webtop was trying to issue sort or search commands.
The same accounts previously worked with Thunderbird clients and/or RoundCube interface, never facing this problem.
Digging into the issue, we compared the imap protocol produced by Thunderbird, RoundCube and Webtop, discovering
that JavaMail is internally all based on message numbers, so any sort/search/fetch is a normal SORT/SEARCH/FETCH,
while RC and TB always use UID SORT/UID SEARCH/UID FETCH.
We tried to convert our code to use UIDs instead of msgnums, but turned out to be a huge rewrite of JavaMail, because
of how JavaMail imap implementation is tied to msgnums.
So my questions are:
- is it a known fact that Dovecot prefers and performs better with UIDs than with msgnums?
- is there any tweak we can do on Dovecot to work better on msgnums?
- anybody already faced this issue with JavaMail/Dovecot?
Thanks for any suggestion,
Gabriele.