When the intended recipient does not receive an e-mail and it is sent back to the sender, it is said that the e-mail has bounced. The sender receives an error message to that effect. But what exactly happens when an email bounces?
When an e-mail has been sent the sender e-mail system makes contact with the recipient mail server. The mail server checks for any message to allow or disallow such a mail to pass through. Some of the circumstances under which an email bounces are these:
Hard Bounce:
- The mail server has barred receiving of mails from the senders address. (For example, if the address of the sender is blocked.)
- The recipient mail server is too busy to handle the request.
Soft Bounce:
- The e-mail address does not exist on the recipient mail server.
- The e-mail address is erroneous or miss spelt.
- The recipient exists but does not have enough disk space to accept the message.
- If the message size is much bigger than the message size pre-decided by the server.
Sometimes, an e-mail may bounce back due to network failure on the recipient server.
