Slaying Your (Mailer) Daemons and Reducing Email Bounces

Slaying Your (Mailer) Daemons and Reduce Email Bounce Rate

You have a huge deal to close and all you need to do is send a very important confirmation email to your client.

Despite the urgency, habit (and prudence) tells you to check and recheck your email, making sure it’s perfect. Then you push the “send” button.

You heave a combination sigh of relief and accomplishment, and when you close your eyes, you imagine confetti falling all over as you enter your office the next morning, everybody chanting your name like you’re some god, and the boss is smiling from ear to ear like he just got promoted to CEO. You’re the man of the hour. No, you’re employee of the year!

But before you leave the office, you check the “sent mail” section just to be sure. Before you can even click on that section, you see a new message.

When you open it, there’s a brief notice from some guy named Mailer Daemon telling you that your email was not delivered because of some problem. Just like that, you’ve been brought back down to earth and punched in the gut, too.

Sounds familiar? Yes, because anybody who’s ever sent an email must have been on the same sticky situation at least once. Lucky you if you’re one of the few who haven’t. But admit it, instead of getting to the root of the problem ourselves, most of the time we just call the tech guy to tinker with the settings.

You know what, no need to call the guy from IT. Here are the three W’s and an H you need to know to slay this Mailer Daemon.

What is it?

Girl with evil costume

A Mailer Daemon is an automated error report from the email delivery system ( that indicates that there has been a problem in delivering your email to its destination. If you receive this error, your email message will be returned to you along with an outline of the delivery problem. In short, it has bounced.

When does it happen?

The most common cause for receiving a mailer-daemon message is an incorrectly addressed email. An email address in general must be typed correctly with no spaces and with the @ symbol in the correct place, for example,

When considering an AOL email address in particular, the screen name is the part of the email address that appears before the @ symbol, i.e.,

Valid AOL email addresses cannot

  1. Be shorter than 3 or longer than 16 characters.
  2. Begin with numbers.
  3. Contain punctuation of any kind (such as periods, underscores, or dashes).

Related: 7 Stats That Proves Email Marketing Is Still The MOST Reliable Channel [INFOGRAPHIC]

Why does it happen?

Once you read the mailer-daemon error report, you will know why your email was returned and how you can avoid such circumstances in the future.

The five sections of the error report are:

  1. The first section tells you when (date and time) your email was received by the mail system. “The original message was received at Tue, 14 Jul 1998 20:48:05-0400 (EDT) from [x.x.x.x]”.
  2. The second section will be a brief message from the Postmaster. The line begins with ” <<<” describes the specific reason your email could not be delivered. The next line contains a second error message that is a general translation for other email servers. *** ATTENTION*** Your email is being returned to you because there was a problem with its delivery. The (client) address that was undeliverable is listed in the section labeled: “—– The following addresses had permanent fatal errors—–.” “The reason your mail is being returned to you is listed in the section labeled: —–Transcript of Session Follows—–.”
  3. The third section has the heading ” —–The following addresses had permanent fatal errors—-.” Here, you will find the address(es) that the email could not be delivered to.
  4. The fourth section is the most important in terms of determining why your email could not be delivered because it contains the specific error because of which the email could not be delivered. “—– Transcript of session follows —– … while talking to >>> RCPTTo:<><<< 550 Mailbox not found 550 <>… User unknown.”
  5. The last section is ” —– Original message follows —–.” This contains your original email that is returned to you as undelivered.

How do I manage/reduce bounces?

  • Do not buy, rent or harvest email addresses. You can’t be sure of the quality of such lists. There is high risk of getting blacklisted after hitting a spam trap. Here’s where.
  • Use a confirmed opt-in process. Many studies show that a single opt-in process is not enough to get a quality list. To be sure that each user on your list is valid, make them confirm their subscription to verify their email address.

Related: 5 Actionable Email Marketing Templates you can use Now

  • Verify your existing list. If you have not emailed your list for a long time, it makes sense to check it for validity before sending the message to it. It may happen that a part of emails are no longer valid. 
  • Remove hard bounce emails and email-generated spam complaints immediately. If you keep emailing to hard bounce and complaining addresses, you risk having all of your future messages blocked. 
  • Monitor delivery by domains. If you see that only a specific ISP is blocking your emails, you can investigate the root of the problem and go through the removal process.
  • Remove repeated soft bounce emails. You’ll want to separate soft bounce emails from your main list and send a reactivation campaign to them.
  • Allow users to change their email address with you. People can change providers, companies and thus, abandon old email addresses and get new ones. So, if you allow subscribers to update their email in your base, you’ll retain more customers and stay in good standing with the ISPs. 

Related: Is Bad Data Hitting You Hard? Here’s How to Roll with the Punches
Email Marketing Series: How to Make Emails your Impossible to Ignore [Video]

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