Security Cert Error

Hi i have set up emclient with a supanet email account but every time i click send it comes up with an error regarding the security cert for supanet saying name miss match. i click remember my choice and connect anyway as i know it is the right cert. but this comes up every time i try to send mail - really annoying - any ideas ? 

Is the message coming from the server, or is this an encryption/signing key error?

A screenshot would be useful.