Perry Hutchison <phutchis(_at_)beaverton(_dot_)windriver(_dot_)com> writes:
IMAP unique IDs are not globally unique, unlike POP3 UIDs. Also the
Unique IDs are not consistent between sessions (they are usually just
the message number in the mailbox which will change with an expunge).
The tuple (IMAP UIDVALIDITY value, Folder, UID) is unique
however. That's why there is a UID in addition to the message number.
Unique, yes, but not sufficiently persistent for the OP's purposes
(as covered elsewhere in the thread). UIDVALIDITY can change from
one session to the next, and at least in the case of the UW IMAP
server, it does change with every new session.
UW IMAP server is something I stopped using because the maintainer did
not handle earlier security incidents properly ("we don't fix exploits
that happen outside root mode" or something similar to that, in response
to an exploit that gave any logged in user a shell regardless of the
passwd /sbin/nologin entry...)
Dovecot's UIDVALIDITY persists between sessions. I'd think Courier's
persists, too.
There are at least four well-respected IMAP server alternatives for
Unix:
BincIMAP
Courier-IMAP
Cyrus-IMAP
Dovecot
BincIMAP, Courier-IMAP and Dovecot support Maildir (no lock contention!)
Dovecot supports mbox format, Cyrus-IMAP has its own store format.
BTW, according to http://www.washington.edu/imap/IMAP-FAQs/index.html
section 6.14, the "DON'T DELETE THIS MESSAGE - FOLDER INTERNAL DATA"
(that can not be seen with UW IMAP server or client software, but can be
seen if you read the mbox file with less or mutt) is supposed to store
UIDVALIDITY information, "[...] Second, it holds mailbox metadata used
by IMAP: the UID validity, the last assigned UID, and mailbox
keywords. Without this metadata, which must be preserved even when the
mailbox has no messages, the traditional UNIX format wouldn't be able to
support the full capabilities of IMAP."
That raises the question whether the mailbox has been damaged during
testing. For instance, a POP3 retrieval from the same mailbox with
another POP3 server than ipop3d may have killed that "FOLDER INTERNAL
DATA" mail, causing UIDVALIDITY to be bumped.
--
Matthias Andree
Encrypted mail welcome: my GnuPG key ID is 0x052E7D95