The Most Common Causes of Email Bounceback

Few things are more frustrating than not receiving an email or text message, or getting a message that your email could not be delivered. These messages are referred to as “bounceback” messages, and they happen for all sorts of reasons. Today, we will explore why emails don’t get delivered, and the most common reasons why bounceback occurs.

How To Tell Why Your Email Was Not Delivered:

Generally when you send an email, you won’t receive any bounceback message and you can assume that the email was delivered correctly.
If there is a problem, you will receive an email response stating that the delivery failed. These email responses usually include a status code. By far the most common code is 550, meaning that the mailbox was unavailable or does not exist.

Specific Codes and how to resolve them:

Beyond the 550 unavailable mailbox code, there are enhanced codes that give you more information. Here are four of the most common:
5.1.1—Bad destination mailbox address
This usually means that the email was sent to an address that does not exist. Double check that you have spelled the email correctly. Try different spellings of names, for example “Cody” could also be spelled “Kody” or “Kodi”.
You can prevent bounceback to your own email address by creating forwarders with different spellings. For example if my email address were, I might also create a forwarding address of
5.2.2—Mailbox full
This error can occur when a mailbox is full and can no longer receive email. The recipient may want to check their inbox and delete all unnecessary emails. A full mailbox can also be caused by an excessive amount of spam.
5.3.4—Message too big for system
If you try to send a large file through email, the message may be rejected by the intended recipient’s mail server. Video files, high resolution photos, and lengthy PDFs are the files that most commonly get rejected.
Instead of sending these files as attachments, try uploading them to a cloud service like Google Drive or DropBox, and sending a link to the file location instead.
5.4.1—No answer from host
The host refers to what comes after the “@” in the email address. If you get this error, you may want to check the spelling of the host section of the email address. It’s also possible that it can’t be delivered because the recipient may have changed their host or let their domain expire.
There are several other, less common error codes. A simple search in the WestHost Knowledge Base can show you ways to resolve them.