Sadly, many Exchange admins don’t do due diligence and ensure proper maintenance on Exchange Server Certificates!
If an Exchange server (2013/2016) is allowed to expire it’s Certificate and you attempt an CU update, the update will fail and it will leave your exchange server broken!
Prerequisite analysis will complete:
Users of Exchange Server 2013 or later or Exchange Online can’t open public folders or shared mailboxes on a legacy Exchange server Consider the following scenarios:
- You have an on-premises deployment, in which Microsoft Exchange Server 2013 is installed in an existing Exchange Server 2010 or Exchange Server 2007 organization.
- You have an on-premises deployment, in which Exchange Server 2016 is installed in an existing Exchange Server 2010 organization.
- You have a hybrid deployment of Exchange Server and Exchange Online in Office 365, in which the hybrid server is running Exchange Server 2013 or later.