This error message might mean that an email our system attempted to send to you in the past couldn't be delivered successfully. This can happen for a variety of reasons. For example, your mailbox might have been full or your email domain has certain filters in place. The latter happens most frequently with work email addresses.
Don't worry! You can still access your account! If you see this error, shoot our customer support team an email at email@example.com and we'd be happy to help get this fixed for you!