Skype for business CCE multiple SIP Domain Certificate Cals

Assumed that:

- you have 4 active domain names
- users are associated with respective domains. 

(if users are using all respective 4 domain names, YES, you need 4 domains to be associated with CCE)
- A single PSTN Site ( simply put a single location/office) 

Example domains you have;

domain-1.com

domain-2.com

domain-3.com

domain-4.com 

In this case, your public SSL certificate will look like as follow;

Common Name (Subject Name) = accessedgepoolname.domain-1.com. 
SANs = acessedgepoolname.domain-1.com,sip.domain-1.com,sip.domain-2.com, sip.domain-3.com, sip.domain-4.com.

The type of certificate you need is "Multi-Domain (SAN) Certificate" , you may have a look at https://www.digicert.com/multi-domain-ssl/