Thanks Timo. Very interesting and very good by you.

My only followup thought is to ask: Is it possible for an IMAP client to request a server side SORT, but not specify explicitly which date to use, and thus rely on a server side choice of the SORT key? In which case could Dovecot use the Date-header as the default SORT key?

On Mon, 2005-04-18 at 02:35, Timo Sirainen wrote:

On Fri, 2005-04-15 at 15:31 +1000, Emmett Lazich wrote:
> Timo or anyone,
> 
> This may be a bug or maybe a design decision. Either way I am curious
> to hear comments.
> 
> Why do the dovecot-0.99.14 server's .imap.index files contain a cached
> copy of each message's date and time as supplied by the filesystem, as
> opposed to the date and time found in each message header?

There are two dates with IMAP. INTERNALDATE is one and Date-header of
the message is another. The filesystem timestamp that you see cached
in .imap.index.data file is the INTERNALDATE. The message's Date-header
is also cached in the beginning of ENVELOPE data.

> When testing various imap clients (eg. tbird-1.0.2, evolution-2.0,
> outlook2003, squirrelmail-1.4.4) I was intrigued by the behaviour of
> message date sorting. I toggled on/off the use of server side SORTing
> in some imap clients, then started forcing rebuilds of .map.index
> files, and eventually came to the above conclusion.

Server side sorting supports sorting based on both INTERNALDATE
("ARRIVAL") and Date-header ("DATE"). It's client's choice which one it
wants to use.

> For normal dovecot server side processing, this condition (if I am
> correct) may not be a problem, but if someone was to deposit a bunch
> of maildir files firstly into an imap account (bypassing dovecot), and
> if this person (eg. me) did not preserve the filesystem/inode file
> attributes. Then dovecot appears to cache the "wrong" data. What
> happens then is that some imap clients can display wrong date+times in
> the message lists, and some imap clients find that server side SORTing
> does not work.

It all works correctly from Dovecot's point of view, because the
messages arrived in the mailbox at that time..