How to read Email Error Codes

Owned by Marc Miller
May 09, 2018

Purpose

This is meant to be a little guide to cover the most common Email Error Codes you will see in bounce back messages.

In most cases, before contacting help, you will find the reason why the email bounced by looking for a line starting with 550 and reading a little after it.

Most of them are pretty straight forward, but here is a list of some of the common ones:

510/511 or 5.1.0/5.1.1 - Bad Email Address

One of the more common mistakes is entering in the wrong address.

Check with the person you are sending to to make sure the email address is correct.

The message will state which email address it is having an issue

512 or 5.1.2 - Bad Host/Host does not exist

One of the next common mistakes is entering in the @<host>.

A good example is someone trying to send to johndoe@gmail.EDU and not to johndoe@gmail.COM.

The host, gmail.EDU does not exist, and would bounce with this sort of message.

The message will state which email address it is having problems with.

550 or 5.5.0 - Email does not exist

This happens when sending to a server and the mail server can't find the user in question.

Note

Most of the email errors will state what the issue is, and is more tied to minor mistakes or services out of ECI's control.

You can also refer to this SMTP Error list for other error code messages.