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My guess is that when you renewed it dropped your ability to renew the internal names of the server? If so, you may have internal FQDNs configured on your internal URLs. I am not sure which version of Exchange you have but I would recommend checking out these two articles for configuring split-DNS and reconfiguring your internal URLs.
Designing a simple name space for Exchange 2010
https://supertekboy.com/2014/05/27/designing-a-simple-name-space-for-exchange-2010/
Designing a simple namespace for Exchange 2013
https://supertekboy.com/2014/07/08/designing-simple-namespace-exchange-2013/