Hi Hernan, Make sure you have SmarterMail configured within IIS according to
this KB Article, and that the Network Service account is controlling the SmarterMail application pool.
Then go to C:\Program Files (x86)\SmarterTools\SmarterMail\
Right click on the MRS folder, go to the Security tab, and grant the Network Service account full control over this folder. That should fix this error. I hope this helps.