There is no point in many cases. Even if you can verify that the email address is syntactically valid, you'll still need to check that it was not mistyped, and

There is no point in many cases. Even if you can verify that the email address is syntactically valid, you'll still need to check that it was not mistyped, and that it actually goes to the person you think it does. The only way to do that is to send them an email and have them click a link to verify. However, if you still want to validate an email address then use a library. All popular programming languages have email validation libraries. Yes, it's an extra dependency if it's not included in the std lib or the framework you use, but email validation is wrong in 99% of the cases, if you wrote it yourself.