Follow this step by step
- Go to manage rules and add a new rule
- Add name of rule, i.e. 'Spam 1'
- Under 'Add a condition', select 'Apply to all messages'
- Under 'Add an action', select 'Move to' and 'Junk Email'. All the junk will move to this folder
- Under 'Add an exception', select 'sender address includes', and in the next box enter the '@' sign
- Uncheck ‘Stop processing more rules’
- Select ‘Run rule now’
- Click ‘Save’
How this rule works
A lot of automated spam hides the 'from' address, therefore it doesn't have an @ sign. This is why you can't block the spam because there is no visible email address to block.
This rule says move all emails to a dedicated folder, except emails WITH an @ sign. As most legit emails have an @ in their address, they will be safe and automated unsolicited spam mail or any mail without an @ sign will get redirected.
Remember
Check your ‘Junk Email’ folder every no and then to make sure that emails that you want to keep haven't slipped through the net. This shouldn't happen, but its just a due diligence exercise just in case.