Are You Getting Email Returns? Here's Why...

Ever had an email “bounceback” and wondered why? There is a specific protocol to inform you when messages do not (for many reasons) make it to the intended recipient.

Being familiar with how this process works can help you determine the issue and why the email was returned to you.

What causes these messages?

Here are a few of the reasons:

The user gave an incorrect email address – usually a typo.
The user account no longer exists (or is experiencing technical difficulties).
The email box is at capacity (over quota).
A spammer intentionally gave an incorrect return address.
Automated messages (autoresponders) are susceptible to the above reasons as well.

An undeliverable or bounceback message will always explain why the message could not be delivered within the return message. The return message you receive will also include an undeliverable error code. A typical return looks something like this:

The original message was received at Thur, 18, March 2021 18:45:05 -0500
(EST) from domain.isp.net [207.69.XXX.XXX]

—– The following addresses had permanent fatal errors —–

—– Transcript of session follows —–
… while talking to mx.domain.or.xx.:
>>> RCPT To: [fake, wrong or erroneous email will be here]
<<< 550 … User unknown
550 … User unknown
</END>

Messages Will Vary

These messages vary depending on the systems involved in email delivery. For example, if you have automated responses engaged. When a spammer sends you an email, your autoresponder will likely bounce back due to the spammer’s bogus address.

At the top of each undeliverable email is a code detailing the reason the network was unable to deliver your email. Here is a list of some of the most common error codes you may encounter when you find bouncebacks in our inbox.

421 Service not available, closing transmission channel
450 Requested mail action not taken: mailbox unavailable
451 Requested action aborted: local error in processing
452 Requested action not taken: insufficient system storage (mailbox full)
550 Requested action not taken: mailbox unavailable (mailbox not found, no access)
552 Requested mail action aborted: exceeded storage allocation (mailbox full)
553 Requested action not taken: mailbox name not allowed (mailbox syntax incorrect)
554 Transaction failed (timed out, resources, network issues)

Many undeliverable emails are due to a simple typo in the email address. Second to that comes spam. And if your email is spammy, it may trigger spam filters that can cause the server on the other end to reject that email.

In most cases, when you take the time to look at the top of the returned email, you will find exactly why the email bounced. Then you know what action, if any, you need to take.