[UX] Notify user on likely email address typo

Summary

A security researcher let us know about a useful enhancement to our user experience: notify users when we find a likely typo in an email address, for example, [email protected] likely has a transposition of the a and the m in gmail.com. While it is impossible to check every domain, we can catch a significant number of typos by checking the top public email services like Gmail, Yahoo Mail, Hotmail, Outlook, and various ISP emails, which could save some of our users a few frustrating minutes.

It is unusual for bug bounty programs to award a bounty for reports like this, but we felt that @ashishag29's contribution made our service more secure and wanted to recognize that work. In addition, this report was prematurely closed and @ashishag29 showed patience and worked with us to help us understand the issue so we decided to award a bonus as well.