Here is the Situation –
Android phone is not Configured with a PIN .
It means . When you unlock the phone . you directly go inside the phone . without any authentication PIN
Now after Configuring a Exchange 2013 Mailbox . you are forced to set a PIN when your mobile device policies is configured in such a way.
So that when you unlock the phone. you are forced to enter a PIN every time.
Now how to disable this on Exchange 2013 Server ?
Login to Exchange Control Panel (ECP) –> Mobile –> Mobile Device Mailbox Policies
Double Click on the default Policy –> Uncheck “Require a password”
Note: By Default its unchecked.