Obviously this only works if all emails to john@gmail.com and john+unrecognisedidentifier@gmail.com are rejected without notifying the recipient. This was how Y

Obviously this only works if all emails to john@gmail.com and john+unrecognisedidentifier@gmail.com are rejected without notifying the recipient. This was how Yahoo's scheme worked (I never actually used it, not sure if it's still active). If gmail's doesn't, then I agree it's worthless.