Web Conferencing: Target Principal Name is incorrect

ProblemWhen accessing the meet url from outside the corporate network you get the error Server error 500 - Target Principal Name is incorrect

Cause
When you tickle the TMG rule the traffic is redirected to the Lync FE, however the requested URL [eg.https://webconf.lynclab.co.nz/meet/john.bravo/9c6gsa] needs to be in the internal FE cert...

Solution
Simply update the cert. So the internal cert will need webconf.abc.com, when youo run through the cert wizard on the FE it will auto populate the cert accordingly