I tried to setup an on-premises server to test the federation connectivity between an online and on-premise user. However, after I setup the server and applied the cert. It shows the incoming connection from lync is rejected in our sever. The error message is "The peer's FQDN or IP address is not recognized by this server 0xc3e93d69" / "SIPPROXY_E_CONNECTION_UNKNOWN_SERVER" from sipfed0f.online.lync.com
I research from web and nearly most of the issue are came from the other federated domain. However in my case it is came from O365 which I cannot alter their certificate. May I know what I should do to allow the incoming sip request to make the TLS handshake?
It is most likely not a certificate error, as the error message says "The peer FQDN or IP Address is not recognized...", but you need to verify you have the necessary root certificates installed in the Trusted Root store on the Edge server (Baltimore CyberTrust Root).