Can’t remember email I used to sign up with

[Judy Jetson]

Can’t remember the email I used to sign up with

[Chris Buzon]

If you mean here in the community site, it's in your personal settings. If you mean on JIRA/Atlassian in your company - that's found in the Admin area under user management, 

You'll need an admin from your instance to let you know which email you used.