Exchange 2016 Out Of Office ( Server Not available ) + Teams Calendar not working.

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Just some info for anyone who uses Exchange 2016 on premise.

 

Had a problem recently where out of office reply's wasn't working correctly, was very touch and go and most of the time you would get "Server Unavailable"

 

But the main issue was Teams calendar which is linked to onsite exchange via the oauth method . That wasn't also syncing most of the time

 

Most research will make you think its an exchange setup error ( most information out there is for setups where it doesn't work at all )

 

Checking the event viewer, there will be some errors in System with the source being "WAS".

 

Solution

 

Either myself or the recent updates i installed ( plus the temp security patches for that latest vulnerability ) put on the following software "Microsoft Exchange Web Services Managed API 2.2" this caused all the issues !

 

You can remove this as Exchange has its own version in the "Bin" directory.

 

Hopefully this will save someone a morning of issues !