How can I unlock my samsung account if I don't remember my original email

[AC Question]

Someone tried to make the phone new by using factory reset and now the phone is asking for original samsung email and password and I can't remember either one

 

[Rukbat]

Go to Samsung, click on "Forgot Password" and try all (how many can you have?) your email addresses. The one that gets a positive response from the site is the address, and you'll get an email at that address to reset your password.

Then get a password safe (I use Keepass2Android Password Safe because I can keep the data file on Drive and access it from all my devices, so there's no "sync" - they always are) and start keeping track of your site addresses, logins and passwords (you'll just have to remember one to get into the password safe).