This is a strange thing when you are change the external certificate for Lync 2013 Edge server. We did for a customer changed from Geocities to Comodo certificate.
After that we got this strange error in the Eventlogg: Event ID 14428, LS Protocol Stack
TLS outgoing connection failures.
Over the past 8 minutes, Lync Server has experienced TLS outgoing connection failures 18 time(s). The error code of the last failure is 0x80072746 while trying to connect to the server
Then I did a lot of search on uncle Google, but I was not able to find any solutions to this issue.
Until.....one of my CoWorkers who is an P-TSP on Office365 here in Norway named Thomas Stubergh, he asked me to check if the Comodo certificate was under Intermediate on the server.
It was not, well then I just downloaded the Intermediate from Comodo and installed it.
I also installed the Intermediate certificate from Comodo on the frontend server.
Restarted the Lync FrontEnd service and restarted the Lync Access Edge service.
This as far I can see this solved my problem
Then we had an problem so that replica between FrontEnd and Edge server stopped. Here we did 2 Things:
First we did this: http://social.technet.microsoft.com/Forums/lync/en-US/2afc4605-cf9c-4ffd-9159-b8523849eab8/lync-2013-edge-replication-is-not-working-after-migration-from-2010-?forum=lyncdeploy
Did not help. Then we did this:
and we rebooted the Edge server and it worked.
Thanks to Thomas Stubergh and Thomas Poett (Lync MVP) who fixed this issue.