Overview

A SAN certificate is one certificate that covers multiple domains, i.e. www.example.com and mysite.org. These are commonly used with Microsoft Exchange and can be used on IIS 7.5 and lower (which doesn't support SNI) if you can't get a new IP address for each binding.

Microsoft Exchange

See this page for detailed instructions how to Create a SAN certificate for Microsoft Exchange 2016, 2013 & 2010.

Caveats!

It should be noted that only one domain will be used in the certificate's Issued to field. So if you create a SAN for www.example.com and mysite.org, people visiting and checking the certificate on mysite.org will see it was issued to www.example.com.

All domains will be visible in the certificate's Subject Alternative Name field. So anyone viewing the certificate will be able to see all the sites included.