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I am building a C# application where users creat an account and type their email address, I know how to validate it with Regular expression, what I am having truble with is how to check if that email actually exist? i.e. lilush@gmail.com --> is there such email address?

Thanks!

user458695
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4 Answers4

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The only way to check this is to send an email to that address and make sure that you send a link that needs to be clicked to activate the account. There is no other way to check if an email is correct

Oskar Kjellin
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4

Have a look at EmailVerify.NET

EmailVerify.NET is a powerful Microsoft .NET software component that verifies e-mail addresses with various tools, including:

  • Advanced syntax verification, according to IETF standards (RFC 2821 and RFC 2822, among others)
    • DNS validations, including MX record(s) lookup
    • Disposable e-mail address (DEA) validation
    • SMTP connection and availability checking
    • Mailbox existence checking, with greylisting and temporary unavailability support
    • Catch-all testing
CD..
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There's only one way to do that: Send an email containing a (unique, of course) link to the address, and ask the user to click the link.

Jorn
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If you wanted to be really fancy you could embed an image in the email as-well. When your server detects that the image was downloaded then you know they opened the email. This also removes the need for the clicking a link thing which many people either don't trust or it doesn't work. Just a thought.

Mitchell
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