[Dovecot] Question about pop3_reuse_xuidl

[Timo Sirainen]

On Tue, 2011-11-15 at 16:02 +0100, Urban Loesch wrote:

> At the beginning of our migration we didn't set the "pop3_reuse_xuidl" configuration option to yes.
> Do you know what happens when we activate the "pop3_reuse_xuidl" option on our running dovecot?
> 
> Will Dovecot change the uidl value for all existing mails which have set "X-UIDL" in its mailheader,

Yes.

> or does Dovecot only change the uidl value for new received and still not downloaded mails?

Nope.. There is pop3_save_uidl=yes setting, which would do this for
Maildir, assuming the POP3 clients had logged in while this option was
enabled, but this isn't implemented for dbox. The biggest problem with
implementing this for dbox would be that it has no variable length
permanent per-mail storage (Maildir's dovecot-uidlist equivalent).

One way to solve this would be by patching dsync a little bit, and then
dsyncing existing mdbox to mdbox-new, which adds existing POP3 UIDLs as
dbox metadata. Those will override X-UIDL: headers. The patching would
be basically by making dsync/dsync-local-worker.c
local_worker_msg_get_next() always set data.pop3_uidl variable to the
correct UIDL (which would depend on your pop3_uidl_format setting -
pop3/pop3-commands.c:pop3_get_uid() shows how).