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

[Ariel Biener]

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
> 
> 
>