In many cases, it is possible to know about known or unknown email address when if you use Mail_CheckUser.
Check Email address
Please input the mail address to below and click on a button.
(The test is possible up to five times.)
Important
This server added SPF records for DNS.
You should add this SPF record to your domain's DNS configuration.
If you don't, the response of 5xx might be returned also to the existing address.
(e.g hotmail and other)
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