setup email account automatically fails with username password error on device for internal mobile devices. (Android and Apple)

I have an issue where laptops can connect inside and outside of my network, also mobile devices such as Android & iPhone CANconnect outside without entering in server name and domain..... but if a user is on the LAN and tries to connect I get username password error on the device.
If I go ahead and manually enter in the username,password,domain.....it works perfectly both inside and outside

this is a new install of exchange 2013 in a lab environment for the purpose of getting my MCSE

​I really don't think it is a DNS issue because I can browse to the site (inside and outside using the external URL's) I am open to correction

I don't think it is a firewall issue as my pervious lab worked without issue and I have changed nothing (its a Cisco asa 5505)

I am new to this so I would appreciate any and all help

Thanks

Shane

Shane Kearney