We recently installed a brand new Exchange 2010 server in an environment that was (well, is until cutover) using POP3. The clients are a mix of Outlook 2007 and 2010. When opening Outlook for the first time, we get an SSL warning for the FQDN of the server's internal domain name (ex. mail1.internaldomain.org).
We have a valid UCC SSL cert for a few domains, including just the server name itself (ex. mail1, plus mail.externaldomain.org, mail.domainsecond.org, etc). However, we could not add the Subject Alt Name for mail1.internaldomain.org, the INTERNAL Active Directory domain, as "internaldomain.org" was already in use on the Internet and we have no control over accepting the SSL authorization/acceptance requests. This is one reason I don't like using A.D. domains that don't end with .local.
On the Exchange 2010 server, there are 3 certs. Two are default self-signed certs and then there's the 3rd party UCC cert. One of the defaults is for mail1.internaldomain.org.
Anyway, is there any possible way to prevent this SSL warning? We are about to cut this office over to using the internal on-premise Exchange server but this "error" will annoy the end users in a huge way.