I am very sorry for the inconvenience; if you were affected, you can reset your email back to the previous address that you want to use.
You can't if your account address is not valid anymore. When my account was created in 2004, I used the e-mail address I had back then. About ten years ago I switched my provider and the e-mail address I used to register got invalid. I should/could have updated it, but never did. I didn't even know my old address was still in my profile.
Today the forum wanted me to confirm my old invalid e-mail address, which of course is impossible. I was still logged in, but you can't change your e-mail address before you renew your account. To renew your account, you first need a valid address in your profile.
There is only one way to get around this problem:
1. If you are logged in, change your e-mail address in your profile and save. The forum does not allow to save any changes before you renew the account, but the change is kept for the current session
2. Refresh browser window. You still can't change and save your address, but the renew e-mail now goes to your new e-mail address if you click on the renew window. Send the e-mail to your new address.
3. Do NOT click on the renew link in the e-mail while any GTP window is open. Close every GTP browser window, THEN confirm the e-mail from GTP
4. Now your account is renewed, you can change and save your e-mail address in your profile