Edit the default recipient policy to change email addresses

So your user account is first initial lastname but you want the email address to be just the first name, ok.

Open ESM- Recipients-Recipient Policies and edit the default policy. Then under E-Mail Addresses (policy) edit the SMTP address to be:
%g@domain.com for it to be firstname@domain.com
%g.%s@domain.com for firstname.lastname@domain.com
%1g%s@domain.com for first initiallastname@domain.com
You can create multiple addresses at the same time as well by clicking new.

Give users a bogus proxy server and remove the ability to change it

Create a group policy called No Internet or something along those lines. Create a security group and put the users that are not going to use the internet in that group.
Edit the rights of the policy so authenticated users don't have a check in the box to apply the policy but add your new group to the policy and make them apply the policy. Next edit the policy:
User Configuration:
Policies-Windows Settings-IE Maint-Connection Proxy settings and give it a bogus IP address.
Admin Template-Windows Components-Internet Explorer-IE Control Panel and Disable Connections page.

This will prevent users from getting out on the internet and prevent them from turning off the proxy settings.