We have a Federation Certificate that has expired on Sept 8th, 2021. I'm assuming if it expired, something would be broke? But, I, nor anyone else has seen any issues or reported any. Is there another certificate that it may possibly be using? From what I understand, this is for calendar free/busy. This was all set up by an employee who is not with us anymore and when we switched to Hybrid environment. Also, when going through Microsoft documentation on renewing an expired certificate, it says that one has to remove the trust and add it back. Isn't it possible to just add a new cert and assign the federation service to it? Sorry for the questions, but I am kind of lost. Thank you for any help! Much appreciated!