A question that comes up frequently in Exchange 2007/2010 implementations is do I really need a UC Certificate? A Unified Communications certificate, aka a SAN (Subject Alternative Name) certificate allows additional FQDNs to be attached to an SSL certificate in addition to the common name. The only time a UC certificate is absolutely required is if you are planning on utilizing Outlook Anywhere. Outlook Anywhere attempts to find the Exchange Autodiscover service by trying to connect to https://autodiscover.domainname.com/autodiscover/autodiscover.xml.  Typically nobody wants to use autodiscover.domainname.com as there OWA address so this is where the UC Certificate comes into play. If Outlook is inside your network it looks to the SCP value in Active Directory to determine the location of Autodiscover which can then be set to https://owa.domainname.com/autodiscover/autodiscover.xml using the Set-ClientAccessServer cmdlet. So, if you aren’t using Outlook Anywhere you can get by with a standard single-name SSL certificate and save a little money. If you do need a UC certificate I would recommend either Comodo (www.instantssl.com) or GoDaddy (www.godaddy.com). Both are relatively cheap and are supported by most devices.