This is the first time I've installed / setup / used 3CX telephone system and this is being setup for test purposes to see if this will replace our current telephone server. I've installed the unix os and ran through the basic settings. The server is from in a HyperV VM with 128gb of disk space and 16gb of RAM allocated. As per the recommendations the MAC address of the local servers adaptor has been made static on the VM and time synchronization service has been unchecked. Host server has its firewall profiles turned off. The 3CX phone system is the free / test version. First thing to note is SIP Trunks, I've not configured any yet as the initial test is for internal use only. Will add those later assuming everything else goes well! First issue - Provisioning phone, we have Yealink T38G phones here, I followed the instructions for firmware / factory reset etc. after a few tweaks (as my current PBX tries to intercept the provisioning requests) got the phone connected to the 3CX phone system but with no service? (Registration failed) I've looked at the general settings on the phone and system (IP addresses / accounts / passwords etc.) but they all seem fine. Any ideas on something I've missed. Second issue - Connecting to our internal server, we have Exchange 2016 running. I've added in the internal IP address / external address / internal address but when I test I get the following message: "The remote certificate is invalid according to the validation procedure." As I'm not sending out email confirmation I can't get the web client to work either so a bit stuck! This is my first post so hopefully have covered the required information. Thanks.