Empty messages list on servers with disabled THREAD command

[SKaero]

Currently if a mail server doesn't support or allow threads when you set it to view threads it shows the message "No messages found in this mailbox" and doesn't show any emails witch is a little misleading. It would be better to just show a message that says its not supported and not switch to the threads view.

[alec]

I don't see a possibility to set threading on server that doesn't support it. COuld you provide steps to reproduce or imap debug informations?

[SKaero]

Here is the thread relating to the matter with imap debug info ​http://www.roundcubeforum.net/5-release-support/17-pending-issues/7121-threaded-view-empty.html

[alec]

Courier-IMAP has such option
{{{##NAME: IMAP_DISABLETHREADSORT:0
#
# Set IMAP_DISABLETHREADSORT to disable the THREAD and SORT commands -
# server side sorting and threading.
#
# Those capabilities will still be advertised, but the server will reject
# them. Set this option if you want to disable all the extra load from
# server-side threading and sorting. Not advertising those capabilities
# will simply result in the clients reading the entire folder, and sorting
# it on the client side. That will still put some load on the server.
# advertising these capabilities, but rejecting the commands, will stop this
# silliness.
#
}}}
So, should we be smarter than Courier authors and fallback to FETCH if THREAD/SORT is disabled? Related ticket #1486959 contains solution for disabled SORT.

[SKaero]

Yes I think that would do the job nicely, although it would be nice to have a message to tell the user why there is no threads but I understand that that could be hard to accomplish.

[alec]

Fixed in [2d1d68bc]. In this case error message is displayed.