Complex sentence: Users are given computer-generated codes upon creating an account, as well as a PIN, which, if not written down right away, will be lost forever, as these codes are not even sent through e-mail to the user.
Split into simpler sentences: Users are given computer-generated codes upon creating an account, as well as a PIN, which, if not written down right away, will be lost forever. These codes are not even sent through e-mail to the user.