-I just realize that I can use only one UCC certificate and compile all my other certificates into one nice looking UCC certificate?
-At the moment my ‘Issued to’ portion mentions specific names of the server like Issued to ‘exchange3.mydomain.com’ should it like Issued to ‘.mydomain.com’? How and where I can change it so that its '.mydomain.com’
-How many subject alternative names I can use on one UCC certificate?
As my certificates will expire in December 2015, I need to figure out compiling all certificates into one basing upon the questions above.
Yes, you can use Wildcards (i.e: .mydomain.com) in your UCC Certificates. In order to add '.mydomain.com’ you will need to reissue your current UCC Certificate. You can ADD the ‘*.mydomain.com’ as additional subject alternative name, or you can just REPLACE it in the ‘Common Name’ field (CN). Please notice that adding wildcard domains to UCC Certificates have an extra surcharge (see below).
Every COMODO UCC Certificate includes up to 3 domains. If you need more domains, there is a surcharge for each additional domain starting in the 4th domain.
According to the following link, each additional domain costs $35/yr USD and each additional wildcard (*.mydomain.com) costs $399/yr: