How to check the existence of a mailbox?

Question

Mail server

Greetings
The site has a subscription form with an eMail address.
Prompt services for checking the existence of email addresses, ie. than you can check the existence of mailboxes, preferably in bulk, at least up to 50 addresses.

Answer 1

There is no guaranteed check for the existence of an email in bulk.
If you sent a letter and did not receive an error in response - you can assume with a high probability that the mailbox exists, that's all.
But, in the fight against spam, different methods are used.
Refusal to specific addresses, domains (therefore, there cannot be known services for checking the existence of emails - they will immediately be blacklisted).
Analysis of your letter and refusal to parse with suspicion of spam.
Analysis of your letter and complete silence in response to leave less information. In this case, the letter itself can either reach the addressee or go to /dev/null
The only working way is with the active participation of the user. Send a unique referral link in a letter (preferably with an expiration date, for example, a week maximum). If you entered it within the specified period, note that this email has been confirmed.

Answer 2

The most famous and popular service of this kind is 2ip.ru.
But for mass automatic verification, it is of little use, since it begins to require captcha.

Answer 3

I agree with Saboteur about the referral link, but what if the person quit and his account was deleted, and once you send mail to such an address, you will get a whack. It follows from this that you will have to process slaps , which is actually one of the requirements of large mail providers.

Answer 4

There is no such service. And apparently never will be.
And that's why.
When there was no spam yet, everyone behaved honestly, followed the RFC, and having received User unknown in response, you could say with confidence that there is no such user. Now, when spam protection methods are becoming more sophisticated, and spammers' methods, respectively, are also not standing still - there is no guarantee that User unknown means that the mailbox does not exist - it can easily exist and be actively used - but your letter did not pass according to certain criteria , and for you to get rid of - you get User unknown.
In exactly the same way, receiving a letter by the server does not mean at all that the letter has been read by the user. It can be delivered to a bot, it can be killed by an anti-spam filter, it can be stupidly dumped into /dev/null - without any notification. The user could quit a long time ago, and the mail was redirected to another or even simply to the trash.
The only way is to get feedback from the addressee. Let him click on the link - if he has not clicked for some time interval - then ala ulu.
In the current conditions, mail cannot be a business tool - there are too many factors that do not depend on the current moment for a letter not to reach.

Answer 5

Also searched. found software. testing.
Email Verifier
https://www.maxprog.com/site/software/internet-mar...

Answer 6

Service for bulk checking email mailify.ru
For yandex .ru @gmail.com you can check, for @mail.ru it always answers that it exists, such a feature of the mail.