The documentation for the GroupMembers Add method states that "AddressBookEntry objects must have a valid e-mail address."

What constitutes a valid e-mail address and how is this checked?

The reason I ask is that if I try adding a new AddressBookEntry with and email address ending in ".net", I get an error message that "an invalid argument was passed in the function call". If I switch the email address to a ".com" address, the Add method works as expected.

Is there somewhere to configure "valid email addresses"?