BUG: cannot move messages to root mailfolder in namespace "There can be only one namespace with inbox=yes"

[Marc Roos]

 >
 >> 
 >> I get this error message from apple mail when I right click and 
choose 
 >> archive
 >> "The IMAP command "UID COPY" (to Archive) failed for the mailbox 
"INBOX" 
 >> with server error: Mailbox isn't selectable"
 >> 
 >
 >Did you notice that you have a mailbox called 'Archive' and namespace 
called
 >'Archive'? Namespace roots are not selectable, and this looks more 
like a 
 >config error.
 >
 >

That is been done on the advice I got here. 
Since November I am trying to get resolved, that I need my Archive and 
subfolders on different storage location as the default. Furthermore 
Archive folder is being used by apple mail, Archives folder eg. by 
Thunderbird. So it would be nice to 'group' this, so Thunderbird is not 
accidentally storing this on the default storage.

If the aliases plugin was working properly, I could have done this maybe 
via aliases
https://www.mail-archive.com/dovecot@dovecot.org/msg75587.html