Exchange 2013 - about to have a nervous breakdown!!!

[mdrabble]

Installed Exchange 2013 all working well except for SMTP spoofing in the internal domain -

 

Some users are getting emails from themselves which they haven't sent. - so having looking at this - If I remove anonymous users from the Receive connector then it stops - BUT emails from Google, Icloud, etc.... bounce back as they are not authenticated.

 

So..... anyone else have this issue??? Or better still..... how do you have your exchange configured?

 

Cheers

Mark