exchange 2016 APM S4U Issues when AD domain and Email domain differ

Guys

 

I am wondering if you can help. I am currently deploying a green field exchange 2016 deployment through a BIG IP APM/LTM combo. This is two seperate F5 appliances, whereby the first is APM and the second is LTM. I have deployed the solution using the latest Exchange 2016 iAPP however when accessing the services externally I get S4U ticket issues.

 

In this deployment, the internal AD domain, and the external mail domain are two different addresses. For the sake of this I will refer to the AD domain, as AD.LOCAL, and email as EMAIL.COM.

 

Ive added the EMAIL.COM suffix to AD Sites and Services, such that a user is able to login with a UPN of ADDRESS@EMAIL.COM or USERID@AD.LOCAL

 

However I am seeing S4U ticket issues in the APM.log file.

 

DNS is working correctly, and I have setup the SPNs as per the build guide with the correct AD deligation accounts. Ive got to the limits of my knowledge

 

Has anyone had similar problems?