Ethereal is a testing platform for Nodemailer, an 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, all messages are stored to the Ethereal account and no message never leaves the system. So far Ethereal has catched 358 735 emails sent using Ethereal testing accounts.
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.
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.
All account registration is handled from the Nodemailer API. If you have lost authentication details for a previous account, then just create a new one.