What are the certificates can be installed on Exchange 2007 and Name a few commercial CAs?

Wildcard Certificate: Exchange Server support certificates with wildcard names, such as *.nakshatrait.com. This is an acceptable domain. Please make sure that some legacy clients and mobile devices do not support wildcard names on a certificate.

SAN Certificate: This is the most widely used certificate type such as it has one common name like webmail.nakshatrait.com and some additional domain name refer to Exchange other services like Autodiscover.nakshatrait.com, pop.nakshatrait.com, imap.nakshatrait.com.