[Dovecot] dovecot 1.0.15 upgrading to dovecot 1.1.x or 1.2.x, and POP3 UIDL issue

[Timo Sirainen]

BTW. With v1.2.5+ and Maildir you could use pop3_save_uidl=yes. Then
pop3_uidl_format affects only new UIDLs and wouldn't cause redownloads
if it gets changed. Uses of course a bit more disk space and disk I/O.

On Mon, 2009-10-05 at 02:33 +0200, Ariel Biener wrote:
> 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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