SymptomsThe problem occurs on Parallels Plesk Panel (versions 8.6, 9.0) and Mdaemon 9.5 and higher.
ResolutionThe problem is going to be fixed in future Plesk versions.
To fix the issue it is necessary to apply the following workaround:
1. Download and extract required mdaemonproviderw.dll file;
2. Copy "%plesk_bin%\mdaemonproviderw.dll" file to an another location for backup purposes;
3. Copy mdaemonproviderw.dll file to %plesk_bin% folder.