On Jul 12, 2020, at 1:36 PM, Sami Ketola <sami.ketola@dovecot.fi> wrote:

On 11. Jul 2020, at 22.50, Filip Hajný <filip@hajny.net> wrote:

I just created a subfolder in Apple mail. It shows up on the server as .list.Subfolder
I drug your message into the folder, and the message shows up in Mail.app and shows up in the subfolder on the server

# ls -lnR .lists.Subfolder                          [10:40] [/usr/local/virtual/kremels@kreme.com/Maildir]
total 56
drwx------  2 89  89   512 Jul 11 10:41 cur
-rw-------  1 89  89    21 Jul 11 10:41 dovecot-keywords
-rw-------  1 89  89   109 Jul 11 10:41 dovecot-uidlist
-rw-------  1 89  89  1924 Jul 11 10:41 dovecot.index.cache
-rw-------  1 89  89   868 Jul 11 10:41 dovecot.index.log
-rw-------  1 89  89     0 Jul 11 10:35 maildirfolder
drwx------  2 89  89   512 Jul 11 10:35 new
drwx------  2 89  89   512 Jul 11 10:41 tmp

I’ve created a test server and found out that the driving factor is what the namespace `separator` is set to. If set to /, Apple Mail gets confused and URL-encodes it when creating a new folder. If the separator is blank (as set by default) or set to e.g. a dot, everything works just fine.

Based on example and docs I found, a slash character should be good or even recommended, suggesting this is some kind of bug in Apple Mail,  but I’m not versed enough in the IMAP related RFCs to understand.

I'm Apple user. I have separator set to / and I can create folders just fine without any encoding. Can you please record imap rawlogs where it shows what command your Mail.App is sending?

Sami