Implement email address validity detection by programming

ThisVB6COMThe component provides an instant mail query function. It effectively avoids sending emails to a nonexistent account. For exampleASPCheck whether the email address entered by the user is correct, and avoid storing related error information in your user database.

Main Content

Working Principle

Let's first look at how this component works.

FirstEmailAddress (for example:Someone@somewhere.com), And then it will perform the following steps:

1,Change the user name (Someone) From domain name (Somewhere.com;

2,InDNS(Domain Name Server): whether the domain name is available;

3,IfDNSIn response, it willMXFor query (Mail ExchangerEmail Exchange Server), and tryMXEstablish a session until the session is established successfully;

4,UseSMTPProtocol, which usesVRFYCommands andMail handshake(HELO,MAILT FROM,RCPT) To verify the existence of the user name in this domain;

5,The component then returns the test results and provides four possible results:

L"Domain" does not exist. The server makes a negative response.

L"Domain" exists, but the user name cannot be queried (see comments ). The server makes a partial confirmation response.

L"Domain" exists, but the user name does not exist. The server makes a negative response.

L"Domain" and user name both exist. The server makes a full confirmation response.