Ethereal is a fake SMTP service, mostly aimed at Nodemailer users (but not limited to). It's a completely free anti-transactional email service where messages never get delivered.
Instead, you can generate a vanity email account right from Nodemailer, send an email using that account just as you would with any other SMTP provider and finally preview the sent message here as no emails are actually delivered.
IMAP/POP3 Ethereal addresses act as real IMAP/POP3 accounts. You can access sent and received messages using your favorite email client, whatever that happens to be.
Inbound The same account acts as a real inbound email address. You can send emails to that address from anywhere and these messages also end up on the account mailbox.
Automatic All account registration can be handled by the Nodemailer API. If you have lost authentication details for a previous account, then just create a new one.