[Dovecot] Outlook 2013 - mounting folders with XLIST

[Hajo Locke]

Hello,

>> i do some tests with dovecot 2.1.7 and activated a default special-use
>> config. To get it work with outlook 2013, i also added XLIST to imap
>> capability string. basically this is working.
>>
>> is somebody also using special-use folders successful with outlook 2013?

> yes, testet a few times, works fine, without Junk folder , cause
> outlook wants this handled by it own, but i ve seen reg patches to
> change this

My serverside setup now is completed. I did a lot of tests last weeks and 
experienced some strange behaviour of some clients.
Outlook 2013 is only working when adding XLIST manually to imap_capability
imap_capability = +XLIST
This is because outlook 2013 not supports rfc 6154 but the deprecated XLIST 
standard invented by google.
So the problem with junkfolder is not a bug in Outlook 2013, in rfc 6154 
spamfolder is tagged by \Junk, in XLIST standard \Spam is used.
I did see that when using a gmailaccount in outlook 2013.
Adding XLIST capability to dovecot seems to be a problem for other Clients. 
k9 is able to work with rfc 6154 servers. But if k9 finds XLIST and 
SPECIAL-USE together in capabilitystring it seems to prefer XLIST requests. 
Because of dovecot is accepting XLIST requests, but outputs rfc 6154 
details, k9 seems to be confused and dont finds special Folders. rfc 6154 is 
similar but not identical to XLIST.  If you dont test with really individual 
foldernames, you get tricked by clients behaviour.
I looked around and the most imap-servers of hosting companies etc. provide 
XLIST feature, Special-USE unfortunately only a few.
So i did now some changes to dovecot sources on my own.
I added \Spam as allowed special-use attribute and created a new function 
for XLIST Requests. So if XLIST is requested, Clients gets lines of output 
with XLIST and \Junk is replaced with \Spam.
So all is done in the code and i dont need to change my userdb-config. 
Testing this server with different clients was successful. All of them did 
find their special folders and worked fine, outlook 2013 also finds 
spamfolder now. So this changes contribute to consolidate a deprecated 
standard but i have to find a way where all users can benefit from new 
features.
This is not a request to change something in dovecot, this is a call to 
decision makers to support one rfc Standard.

Hajo