
Ask HN: How hunter.io, rocketreach.co and neverbounce.com verify emails? - quotz
These services can verify whether certain emails exist. How do they do it? It cant be that theyre sending emails and wait for them to bounce?
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jabbslad
From [https://hunter.io/email-verifier](https://hunter.io/email-verifier) :-

* Valid format: First, we verify the format of the email address is correct and looks something like "email@provider.com".

* Gibberish Email Address: We check to ensure the address doesn't look like a random email address. For example, 1e49cs1pb6@company.com * doesn't pass the test.

* Disposable Email Address: We check if the email address has a domain name used for temporary email addresses.

* Webmail Email Addresses: We verify if the email address uses a webmail like Gmail or Yahoo.

* Presence of MX Records: We check if there are MX records on the domain. If there aren't, the email address can't receive emails.

* Presence of SMTP Server: This check is successful if we are able to connect to the SMTP server (indicated in MX records).

* SMTP Check: We test the email address and see if it bounces or not, without sending an email.

* Accept-all Domain: We check if the server has a catch-all policy which accepts all the email addresses.

For the "SMTP check", they will be doing something like this, programatically:
[https://www.labnol.org/software/verify-email-
address/18220/](https://www.labnol.org/software/verify-email-address/18220/)

~~~
quotz
So its that simple? Few lines of code?

