[MlMt] Mailmate et Inbox

[Bill Cole]

On 3 Oct 2016, at 16:08, Benny Kjær Nielsen wrote:

> On 3 Oct 2016, at 16:50, Alain Israel wrote:
>
>> Indeed, but I was wondering whether « Important » is part of 
>> these standard keywords, as it could be used as an all purpose tag, 
>> while *flagged, seen, junk* have a specific function.
>
> I don't think so. The Exchange server I have access to has this 
> response:
>
> 	* OK [PERMANENTFLAGS (\Seen \Answered \Flagged \Deleted \Draft 
> $MDNSent)] Permanent flags
>
> This means that the server supports the listed keywords and nothing 
> else. I don't know if this is in any way configurable by the server 
> administrators. I also don't know how/if `$MDSSent` is used by 
> Exchange. Maybe it can be misused to get a single server-synchronized 
> custom tag...

$MDNSent is used to mark messages for which a message disposition 
notification message has been sent. I don't see how Exchange can be 
repurposing that in any way that IMAP clients (which generate "message 
read" MDNs) can work with, since messages themselves have headers that 
indicate the sender's desire for a MDN and the IMAP spec says messages 
(including headers) must be immutable.

Note that Exchange has its roots in X.400 mail, which has an Importance 
attribute for messages and RFC2156 defines that as translating into an 
Importance header in Internet email. There is also a common X-Priority 
header that some versions of Exchange and Outlook use to replicate 
Importance and some clients have even tried to use a Priority header, an 
X.400 transplant that is such a bad idea (transport priority determined 
by sender) that I don't think even Exchange has ever supported it for 
Internet email. However, some clients have conflated all 3 into a single 
Importance or Priority attribute that looks like an IMAP attribute 
(sorta) but doesn't ACT like one because it can only be changed by 
deleting, purging, and re-saving a message with the appropriate 
header(s) changed or absent. Complicating the whole thing further, the 
standard "\Flagged" IMAP keyword is arguably the same semantically as 
having the Importance header being "high" so there may be some systems 
which set that on delivery based on the header.