Please help - can't figure out how to stop insert record on form validation

Hi - can't figure out what I am doing wrong.

Trying to stop duplicate records from being inserted into my table, using 'email' as the key.

I have set up my recordset to check the email, created the form have the validation show if behaviour showing the error if there is a duplicate record.

Even if the error shows, the insert record still puts the record in.

I have been trying using the Rules manager to create a rule that is success if $totalRows_usremails is null (I think?) but just can't seem to figure it out. I then set the insert record behaviour to trigger on Rule: Validation Success but either get header errors or it doesn't work.

Please help! My error messages work but the insert record ignores them!