I have this issue after I updrade to latest i-MSCP version.
When I sent emails from roundcube, all email sent, and stored in Sent folder.
But when I use Outlook, I have an error message, (Email couldn't stored in Sent folder).
Mail sent, but not showed in Sent folder.
i-MSCP version: 1.5.x-konzeptplus
OS: Debian Jessie 8.10