Exchange 2010 co-exist with 2010 accessing 'EAC' for the first time?

I have just installed exchange 2013 co-existing with Exchange 2010.

Looking for the EMC I discovered it is now the 'EAC' which is all now web based.

The URL is now: https://<CASSERVER>/ecp

However if your accessing the 'EAC' with a mailbox that is still on the Exchange 2010 server you need to access it with the URL:

https://<CASSERVER>/ecp/?ExchClientVer=15