I've seen lots fo posts about this but none really address my issue. When entering the email address in a new account setup on any Active sync device it does not auto configure and you need to manually enter the domain name and servername.
Internal autodiscover with AD connect clients works fine. All other External access works fine, once manual servername and domain are entererd.
We have the autodiscover external DNS setup and it is resolable and ExRCA also checks out ok. The TMG rules also seem to be ok.
internal and external url's are set properly on the CAS servers for autodiscover and active sync.
So WTF am i missing as i havent been able to find a clear article on all the components to check