Thank you very much did the trick.
Do you know if there's anyway for the SSL cert to work with everyone's mail, I'll try to explain.
If I set incoming to mail.myhostname.com then the SSL cert works good
But...
If I set it to mail.theirdomainname.com then the SSL errors (which of course it would cause it's not their domain name, but I don't want to have to purchase an SSL cert for every user), although of course the email works if they except the cert.
Thanks again,
Lee.