To activate / adjust mail spam detection level, log into your domains control panel.

Click on “Mail” in the left column.

Click the email address for which you’d like to activate or adjust the spam detection settings. Then switch to the “Spam Filter” tab.

To turn the feature on, tick “Switch on”.

To change the level of spam detection, open the section of “show advanced settings”.

“Spam filter sensitivity”: The lower the number, the stricter the spam detection. However if you go too low, genuine mails start getting detected as spam!
A save bet between good spam filtering without any genuine mails being affected is 4.5 to 5.

Click “OK” at the bottom and you’re DONE 🙂