Email address checker — Three-level validity check
You can use email checker and verify emails in three steps. This three-level validity check gives the most effective results. Each of the three steps can be executed separately, or combined to form one big verification process. The steps are:
Syntax check. This is basic verification. Addresses are checked for correspondence to the RFC registration.
Domain check. The domain’s existence is checked. In the case of a non-existent domain, the email address would also be nonexistent.
Email address check. This is the last step of full verification. Atomic Mail Verifier searches for a domain’s SMTP server and checks the user’s existence.
With such reliable verification, you can exclude as many nonexistent emails as possible. You will also prevent deletion of truly valid emails using an email list cleaning software.