Not necessarily. They also give you a “gibberish” address to the account. So if I use “foobar” as my mailbox on mailinator, they will list an address like M8R-w

Not necessarily. They also give you a “gibberish” address to the account. So if I use “foobar” as my mailbox on mailinator, they will list an address like M8R-wk43th@mailinator too, that does not let people log in.