I recommend not to use invalid one, if you forgot the password then you need email to reset the password if I remember it correctly and sure there's an alternative to go through with staked bitcoin address and signing in a message to prove the ownership in case you can't remember the password and you have been logged out but it can be a long process.

I am using an email that I will have access to all the time but it's not the primary email that I use for the personal use.