We run Exchange 2013 for several organizations. I have a SAN cert with Subject Alternative Names for every SMTP domain as in, autodiscover.domain1.com, autodiscover.domain2.com. Each organization's DNS contains an CNAME record for autodiscover that points to our hosted autodiscover entry. This process worked flawlessly until I needed to create trust relationships with a few organizations. We are not using linked mailboxes in all of these instances.
The problem is that a user logged into their AD Forest on a computer in the same forest can never complete the autodiscover process. If a local computer account is used, instead of a domain account, on the same computer, autodiscover works fine.
My remote connectivity tests pass successfully with either domain or local account.