Free online service checks the existence of a given mail
The service checks if this email address exists and finds social media, web sites and web services where the email leaked.
You can enter the email completely, i.e. in the form of firstname.lastname@example.org, and you can enter only the name (nickname) - in this case, a search will be performed for popular mail services - which ones used this nickname as the mailbox name. And then will be performed search for social media, web sites and web services where the email was used.