logging in

I am not sure if this issue belongs to the OS or network being completely new to servers, I have managed to install and get OMV. working pretty good with a mixture of Mac and Unbuntu users, the one issue I have is that users have been granted read and write privileges and each user has connection as soon as logging on those privileges do not apply until you unmount and remount the drive.
If anyone can offer a solution it would be much appreciated.
Kind regards
Buff