I still find that customers are using self signed certificates for their Exchange servers. When you install Exchange UM and want to link it to OCS you need to use a properly trusted certificate from a CA. To do this requires some messing around in Powershell and can be inconvenient. Today I spotted a blog post from Rui Silva highlighting a Certificate Management Tool from U-BTech which gives a quick and easy GUI to manage the Exchange server certificates. I haven’t tried it yet but I think it is definitely worth investigating.
Exchange 2007 Certificate Manager