[Dovecot] One dovecot, multiple domains

[Ben]

Hey guys, I've got dovecot configured to work perfectly for virtual users across 
different domains. It's great.

My problem is that, as far as I can tell, dovecot makes me use one SSL 
certificate across all my domains. That's not what I want. Is there a way I can 
get dovecot to use the cert for mail.foo.com when somebody is logging into a 
foo.com account, and the cert for mail.bar.com when somebody is logging into a 
bar.com account?

Am I missing something obvious, or asking the impoosible?