Did I get it right? You woke up after three years of inactivity, but now cannot remember your password? How did you know it a few minutes ago? And, you cannot access your email account anymore?
Don't remember password
No access to email
No signed message and a stake it in the forum or at least did not have any address posted on the forum which the member can still access it and sign a message from it. However, to do it, that address must come from a non custodial wallet which allows to sign messages.
Combine them, it's impossible to recover the account.