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  • Writer's pictureArial Software Technical

Bounces - The Wild West of the Internet

Updated: Feb 3

Bounced email is a subject that comes up very often in our tech support department. In this blog we will try to define all the aspects of email bounced and how to deal with them. But first we need a reason...

Dealing with bounced emails is very important. Many times bounced emails are just ignored because it does not "cost" anything to just keep sending to the same email addresses. The problem is that many mail providers like AOL, Hotmail, Gmail are all sensitive to emails sent to them that do not exist. For instance, if you are sending 1000 emails to AOL addresses and hundreds of them does not exist, AOL will consider you a spammer because you are not a "good citizen" and will at some point not allow your SMTP server to send ANY more email to them. When you do this to all the major email providers all the time you can see why many of the emails you send out will just not make it to the REAL end users. So overall, you need to deal with bounces to keep your reputation clean.

As explained in a previous blog, bounces can happen immediately or delayed. Immediate bounces happen when your SMTP server rejects the email the instant it is submitted. These records can be marked as "bad" in Campaign Enterprise and then you would filter these addresses on the next send or just delete them completely. The delayed bounced emails are the tricky ones. Here is how a bounce is generated:

1. You send an email using your SMTP server

2. You SMTP server verifies the format of the email address and accepts the email message into it's queue

3. Sometime later, your SMTP server looks up the MX record for the domain of the email address (like AOL.COM)

4. If the domain does not exist, then your SMTP server sends a bounced email to your bounced email account

5. If the domain exists, your SMTP server now contacts the destination SMTP server

6. The email message is submitted to the destination SMTP server

7. The destination SMTP can immediately reject the email message, and if it does, then your SMTP server sends a bounced email to your bounced email account.

8. If the destination SMTP does accept your email message, it can then reject it later if it finds a problem. In that case, the destination email address will send a bounce email to your bounced email account.

So, from all of this, you can see that the actual bounced email you receive can come from many different sources. The "Wild West" reference in the title refers to this process and also to the actual contents of the bounced email: There are no rules about the content. This makes if very difficult for us. To properly record a bounce we need to know two major things: The original email address we sent to, and what the error was. Sounds easy? Nope. With all the email systems throughout the world, there are that many different bounced email formats, and they change, all the time. So harvesting information from bounced emails is truly an "art" and is a good reason to keep updating your Campaign Enterprise product because we strive to keep up with all these formats.

If you have any questions on this subject please email us at

Campaign Enterprise is a scaleable enterprise-level email distribution system that runs on your own in-house computers connecting directly to your database or CRM in real-time, and using your own mail server. Visit for more information.


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