There's nothing any user on here can help with locked or lost password or lost email accounts that is up to the user to find out what happened to their Email account that they can't get password reset.

What is the "email format" (without giving the user name - e.g XXXX@ ...)?

You could try https://accounts.firefox.com/signin

it is @anonaddy.me

I suppose 'me' is the country code for Montenegro. The address lacks a top level domain, e.g. co, com, net, org. It is possible, apparently, to open a support ticket on Firefox accounts but I haven't been able to find out how.

A top level domain may no longer be necessary.

Try the following sign in site (remove the blank space).

https://accounts.firefox. com/signin