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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