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[Imap-protocol] Microsoft Outlook IMAP non-compliance: negative UIDs

E-mail headers
From: Mark Crispin <mrc@CAC.Washington.EDU>
To: imap-protocol@u.washington.edu
Date: Fri, 08 Jun 2018 12:34:38 -0000
Message-ID: alpine.LRH.0.82.0701241824421.30514@shiva1.cac.washington.edu permalink / raw / eml / mbox 
Microsoft Outlook sends a
    	tag UID FETCH n:* ...data items....
command shortly after opening the mailbox.  This is the typical idiom for 
learning about messages that were delivered since the mailbox was last 
opened, with n being the largest UID determined in the previous session 
plus 1.

There's a problem, though.  Outlook sends n as a *signed* value.  The IMAP 
specification (RFC 3501) is very specific that UIDs are unsigned non-zero 
32-bit values.

Thus, Outlook ends up sending:
    	5mwd UID FETCH -1065616957:* (UID FLAGS RFC822.SIZE BODY.PEEK[HEADER] INTERNALDATE)
when it really intended to send
    	5mwd UID FETCH 3229350339:* (UID FLAGS RFC822.SIZE BODY.PEEK[HEADER] INTERNALDATE)

Needless to say, the IMAP server objects to a negative number as a UID.

This problem exists in "Microsoft Internet Messaging API 6.00.2900.3028 
(xpsp_sp2_gdr.061107-0012)", or at least that's what it calls itself in 
the log.

This sounds like a great way for a site administrator to ban use of 
Outlook; just make the IMAP server assign UIDs starting at 0x80000000.

-- Mark --

http://staff.washington.edu/mrc
Science does not emerge from voting, party politics, or public debate.
Si vis pacem, para bellum.
Reply
E-mail headers
From: tss@iki.fi
To: imap-protocol@localhost
Date: Fri, 08 Jun 2018 12:34:38 -0000
Message-ID: 1169719564.13714.411.camel@hurina permalink / raw / eml / mbox 
On Wed, 2007-01-24 at 18:25 -0800, Mark Crispin wrote:
> This sounds like a great way for a site administrator to ban use of 
> Outlook; just make the IMAP server assign UIDs starting at 0x80000000.

Outlook isn't nearly the only client that has problems with it. Just a
couple of days ago I received a mail requesting that my server
automatically renumber all UIDs once they get over 31bit:

> Some IMAP clients I've tested (Thunderbird 1.5.0.9, SquirrelMail
> 1.4.9a/PHP 4.3.2) appear to use signed 32 bit identifiers and request
> the above message as UID 2147483647 (max signed 32 bit integer).

I'm sure there are a lot more.

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