What is the bounce procedure?
When an SMTP server can't deliver a message to a mailbox, a bounce message is returned to the original sender.
The bounce message is returned with:
With the bounce message
The bounce message may not:
- identify the address that failed.
- include a copy of the original message.
With Variable envelope return path (VERP)
The Variable envelope return path (VERP) 1) is a technique that helps to identify the bounce email address.
Example of sender email address where the sender is [email protected] and the tag is bob=example.org
With DSN (Delivery Status Notification)
With the X-Failed-Recipients
Some SMTP provider adds the header X-Failed-Recipients that indicates the failed recipients.
X-Failed-Recipients: [email protected]