We are on Lync 2013 but many of our clients are using the 2010 client because they have XP. Not experiencing any issues with EWS but I have been reading up on EWS in Lync 2010 and I did have one user that had an issue internally with EWS where the client said EWS not deployed but it fixed itself without doing anything.
Browsing the Internet, I have found that some have populated the internal and external URL's for the Exchange autodiscover virtual directory on the CAS servers. As long as I have been working with Exchange, they have always been blank and I don't see any reason to change them now. So question is if the URL's are blank, how is the Lync 2010 client working so well and I have no issues with EWS?
I do have an autodiscover.domain.com A record in DNS for our SIP domain. It points to a VIP of our load balancer which directs the traffic to Exchange CAS servers. Are the clients using that?