What are different scenarios for verifying Email address?

In order to verify email address, the front end tester should consider foll owing criteria:-
Email address may contain alphanumeric characters as initial portion, special character allowed are dot (.), underscore (_), in initial portion, there should only be single @ symbol separating local part and domain.
Domain name may end separating dot (.) with net, org, com and edu as well as country specific characters eg. In for india, ca for canada.