Metrics Mayhem: Why Your Emails Are Being Rejected

Whether it’s in life, love, or email, rejection is never an easy thing to deal with. I’ll save life and love for another blog post, but rejected email messages are no different. Rejection hurts, especially when it comes to inbox placement. The first question after a message is rejected is often “Why me?” The hard truth is it’s not you; it’s most likely your sender reputation.

Let’s start with the basics: Rejected mail is a subset of bounced mail, and includes only those messages that fail to get delivered due to reputation issues (user complaints, hitting spam traps, blacklisting, and/or high percentage of unknown users) before they reach the gateway and any filters. Reject rate is an IP-based metric that is calculated as the number of messages rejected divided by the number of messages sent.

There isn’t a silver bullet when it comes to improving reject rate, and the drivers behind them can take time to correct. The important thing is to learn what those drivers are and how to mitigate them to keep your mail in your subscriber’s inbox. Let’s take a closer look at the drivers behind rejected mail:

  1. Complaints: Reports of unsolicited mail (spam/junk) from end-users. Here is more information on complaints.
  2. Spam traps: Email addresses set up with the intention to flag “spammy” activity. Here is more information on spam traps.
  3. Unknown users: Shut down, misspelled, and invalid email addresses. Here is more information on unknown users.
  4. Blacklisting: Being added to a list of IP addresses considered to be sending “spammy” material. Here is more information on blacklisting.
  5. Content: Test to see if certain content and URLs are resulting in a high level of end-user complaints and if they are frequently bulked. If either case exists, it may be time to update and test new content. My colleague, Mary Sohn, put together a health check for content and how it relates to complaints.
  6. Authentication: Matt Moorehead explaines SPF, DKIMand DMARC in plain English in his posts. The main takeways for you are to make sure your SPF record is valid, up to date, and refers to the sending IP; check to make sure your DKIM is functioning correctly; and protect your brand from spoofing with DMARC.

Below are two tools you can use to monitor reject rates and other contributing drivers to your reputation: is Return Path’s comprehensive reputation database covering email senders worldwide. This tool provides an overview of health metrics, including reject frequency displayed as “High” or “Low” and IP address reputation rated with a score between 0 and 100:



Return Path’s Reputation Monitor is available for most Return Path customers and provides an in-depth look at reputation drivers, including sender rejected rates and customizable performance graphs:



Seeing an increase (or decrease) in reject rate is often the result of a change to your sending practices. Remember to consider the drivers behind reject rate when making changes to your program:

  • Changing hosted email providers (such as RackSpace or can lead to potential authentication issues. Be sure to confirm all the DNS entries are correct before your first send with the new provider.
  • Updating or changing content entirely (or even making small updates) deserves testing. Consider the subscriber experience when changes are made to keep complaints low. When testing, it’s important to track response rates and ensure that the changes being made are effective with subscribers so your reputation stays good.
  • Changes to your send list can have unintended consequences for your reputation. Extending your list to include some older email addresses can lead to a jump in unknown users and spam traps. Remember to consider list hygiene, engagement, and the source of new email addresses when extending your list. If a user has not engaged with your message in more than six, chances are good that they will not engage with it again.
  • Sharing IP addresses or sending on behalf of another entity or partner company can have a detrimental effect on your delivery. Your IP address reputation is only as good as the content, list quality, and engagement of the emails sent from it. Keeping your IP address healthy means more email gets to the inbox.

For more information on common email marketing problems, take a look at our Guide to Email Marketing Metrics.

You know, looking at all the reject rate metrics and thinking about everything that can effect a sender reputation, maybe email delivery isn’t all that different from life and love; you get out what you put in. So keep those sender reputations healthy and your mail will likely hit in the inbox.

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