DIY: Deciphering Email Bounce Messages

While you sit, growling at your monitor wondering just why that message sent to your client was returned “undeliverable” with a long error posted underneath- take a deep breath and read on. We have a handy checklist of what to do when you receive such a message.


E-mail almost never vanishes into thin air. If a problem occurs with delivery, the sender virtually always gets a response, or “bounce”, which consists of

  • a normal header (usually from “Mailer-Daemon” or “Mail Delivery Subsystem”)
  • a section of information specifying what went wrong, and
  • an optional section consisting of the original mail item

Why do we receive error bounce messages?

Errors can occur at multiple places in mail delivery. A sender may sometimes receive a bounce message from the sender’s mail server, and other times from a recipient’s mail server. Bounce back messages from the recipient’s mail server are required when a mail server accepted a message that was undeliverable; when a server accepts a message for delivery, it is also accepting the responsibility to deliver a DSN (Delivery Status Notification) in the event the delivery fails.

With the rise in forged spam and e-mail viruses, users now frequently receive erroneous bounce messages sent in response to messages they never actually sent. Modern servers try hard to ascertain that a message can be delivered before they accept it. Sometimes they type in the wrong receiver’s username and they get an e-mail from that, too. (source)

Try these before calling your technician.

Some emails will bounce back due to simple issues you can fix on your own.

  1. Check the spelling of the email address you are sending to. I know, you swear their name is spelled that way, but check twice just to be sure.
  2. Are you connected to the internet? Without internet connection, your emails are headed on a road to nowhere. Check to see if you can browse the web.
  3. Did you leave out the subject in the message? Some mail administrators reject messages with no subject.
  4. Ask the recipient to check their own spam filters. You may be blocked.
  5. When in doubt, forward the bounce message & error to your support technician. This can be vital for solving the issue.
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