no, that is not why I bought this. I use 'snakeoil' certificates for the email services and I do not think the user actually ver sees a difference.
I use the multi subdomain certificate for two web servers I have running on ISPConfig under different subdomain names. One server is 'front-of house' www.chillifire.net
promoting my service, the other one login01.chillifire.net
is actually delivering the service.
Hope this helps.