Thomas Klausner writes:

...

RTFM: http://wiki2.dovecot.org/IndexFiles

Thanks, but I had read this.

I still don't know what they are good for, why they stay there for days and if I can remove them. After all, they are not the caches, but some "transaction logs" (I don't know what this is).

Re-read the page, all the way to the bottom.

Interpreting the last section:

The transaction log records recent changes to a mailbox, and together with the index, gives the current state of the mailbox. This is an I/O optimization so that mailbox states changes are quickly updated without having to compare an entire index file with the last (in-memory?) index. For large mailboxes, this can save a lot of I/O.

It may persist because updates to the indices are not done immediately (again, possibly to reduce I/O), so the current mailbox state is reflected by the index file *and* deltas in the transaction log.

I suspect that you could remove the transaction logs (if you do not use dbox) and dovecot should rebuild them (or more likely, rebuild the indices).

Joseph Tam jtam.home@gmail.com