[Dovecot] dovecot 1.0.15 upgrading to dovecot 1.1.x or 1.2.x, and POP3 UIDL issue
Ariel Biener
ariel at aristo.tau.ac.il
Mon Oct 5 03:33:02 EEST 2009
Ariel Biener wrote:
>
> Hi,
I think I found the problem eventually:
In the dovecot.conf example file, the section explaining
the various UIDL formats is as follows:
# If you want UIDL compatibility with other POP3 servers, use:
# UW's ipop3d : %08Xv%08Xu
# Courier : %f or %v-%u (both might be used simultaneosly)
# Cyrus (<= 2.1.3) : %u
# Cyrus (>= 2.1.4) : %v.%u
# Dovecot v0.99.x : %v.%u
# tpop3d : %Mf
#
# Note that Outlook 2003 seems to have problems with %v.%u format
which was
# Dovecot's default, so if you're building a new server it would be a
good
# idea to change this. %08Xu%08Xv should be pretty fail-safe.
#
#pop3_uidl_format = %08Xu%08Xv
Notice that the UW format at the top is: %08Xv%08Xu , while at the
bottom it is %08Xu%08Xv. So, in 1.0.15 we had it as the top would have
it, while at the 1.1.x/1.2.x instances we just uncommented the bottom.
I must have looked at these files 1000 times.
--Ariel
>
>
> We're upgrading a cluster of servers from v1.0.15 to
> v1.1.x or v1.2.x. It appears that the UIDL generation mechanism
> has changed, and thus we'll be getting POP3 dups with users
> that leave mail on server (which is a nasty practice, I know).
>
> From checking the sources, and performing a number of controlled
> tests in various scenarios, here is the outcome:
>
> upgrade from 1.0.15 to 1.1.x (latest), UIDLs change
> (no change to the mail backend, that is, mbox)
>
> However, the interesting part is that if for example
> I read a mailbox for the first time with the 1.1.x version,
> and then I migrate the mailbox to a different server, running
> 1.1.x or 1.2.x, with Maildir or mailbox the UIDL does *NOT* change.
> We do not have X-UIDL headers in the mailboxes.
>
> I did every possible permutation of these tests. It appears that
> the way UIDLs are created in 1.0.x is different than what is used
> in 1.1.x and 1.2.x. (I am not talking about the format, we're using
> the same format in both, that is, UW compatible).
>
> Since we're a largish site (university), and we have some >60k accounts,
> even the smallest percentage of users who use POP3 and "leave mail on
> server" is a large number of angry staff members landing on our
> helpdesk, which is the reason why we're not migrating.
>
> Has anyone ever ported the UIDL generation algorithm from 1.0.x to
> 1.1.x/1.2.x to maintain compatibility ? Is there some other option
> that I am missing ?
>
>
> --Ariel
>
>
>
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