We're using dovecot-2.1.16 on CentOS (rpm package from epel repo). Maildir format on ext4.

What exactly do you mean by "Dovecot started reindexing"?

Selecting thread sort on the javamail client, the imap process opens all files in the folder and updates the following files on disk: dovecot.index dovecot.index.cache dovecot.index.log dovecot.index.log.2 dovecot.index.thread

The folder has around 5000 mails and the operation takes some minutes (hw is not the bottleneck).

Selecting thread view on Thunderbird or Roundcube takes less than a second, I can't see the imap process doing anything.

Dovecot's normal indexes or full text search indexes?

Normal indexes.

How have you configured everything?

What do you need to know in particular? doveconf output? Maildir infos: # time cat cur/* >/dev/null real 0m4.651s user 0m0.045s sys 0m0.141s # ls -f cur/ | wc -l 4170 # du -sh cur 49M cur

Things go worse with a bigger maildir.

Does Dovecot log anything (especially any errors/warnings about anything)?

No errors or warnings at all. I've enabled the mail_log plugin, but I think it can't log indexing operations.

Thank you.

-- Ciao, Filippo