Oh, I remember how Lync had different maximum message lengths for the first message in a conversation vs subsequent ones. I believe it was using SIP internally and sending your first chat message in a "begin call" workflow, but it was always unpredictable when a new "call" would start or not. Horrible kludgey solutions...

I want lync back. I'm no longer 20, my eyes demand that I zoom everything in and then features disappear