[Dovecot] Why is "UIDVALIDITY changed" fatal?

[Chris Wakelin]

I've got several users testing Dovecot IMAP at the moment, but some of 
them are also accessing their mail via UW-IMAP at other times. (I've 
warned them about accessing the same folder simultaneously via 
UW-IMAP and Dovecot!) In addition, we have special folders "AutoSpam" 
and "Trash" that pruned using Washington's "mailutil" automatically 
every so often.

Of course, Dovecot's indexes will become invalid in such cases, but 
they seem to get rebuilt automatically OK.

However, in some cases UW-IMAP seems to change the UIDVALIDITY value 
(not sure why!) and when Dovecot tries to sync it notices this and 
gives up with a fatal error on opening that folder. Opening the folder 
a second time is then OK.

I was wondering why Dovecot can't just rebuild the indexes silently in 
such cases (which seems to be done by returning "0" from the 
mbox_sync_loop() routine)?

Best Wishes,
Chris

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Christopher Wakelin,                                c.d.wakelin at reading.ac.uk
IT Services Centre, The University of Reading,       Tel: +44 (0)118 378 8439
Whiteknights, Reading, RG6 2AF, UK                   Fax: +44 (0)118 975 3094