Hi Shalfur. From looking at your checkup page, it looks like the account running the Application Pool is called smartermail. Can you try switching this to the 'Network Service' account, and make sure that it has full control over the following folder:
C:\Program Files (x86)\SmarterTools\SmarterMail\MRS
Afterwards, please restart IIS and then try the web interface again. I hope this helps.