I forgot what email I used for my other ploxtic id: how do you find out what my email was?
The account is user:2078229.
Unfortunately we can't reveal what email you used for privacy reasons. If you lost access to your account, go to https://stackoverflow.com/users/account-recovery and try out a few email addresses.
If all else fails, use the "contact us" link at the bottom of any page to reach us (Stack Exchange support) privately. We still won't be able to just reveal what email you used, but we have a few other things at our disposal then.
That said, hims056 is right - you can sign into your Stack Overflow account the same way you just signed in here on Meta.