AWS Messaging & Targeting Blog

Introducing the Amazon SES Mailbox Simulator

We are happy to announce that Amazon Simple Email Service (Amazon SES) launched the Mailbox Simulator today. In this post we talk about the motivation behind the Mailbox Simulator, how it can help you, and when you might want to use it.

What is the Mailbox Simulator?

The Amazon SES Mailbox Simulator is a set of email addresses. Each address represents a different email sending scenario. There is an email address for:

  • Successful delivery
  • Hard bounce
  • Complaint
  • Out-of-the-Office (OOTO)
  • Address on Suppression List

When you email these addresses, the Mailbox Simulator provides a typical response (or lack of response, in the case of a successful delivery). In practice, the exact format of the response varies by ISP, but you can expect the Mailbox Simulator to provide responses compliant with RFC standards. For more information about the scenario that each email address represents, see the Amazon SES Developer Guide.


Until now, testing your application’s response to various scenarios required some creativity and presented a number of challenges. To create a hard bounce, you could email an address you made up. To test a complaint, you might have sent an email to yourself and then marked it as spam in your email client. These methods, however, required extra work on your part and could be especially tricky if your account was still in the sandbox. For example, in the sandbox, you can send emails only to addresses that you have verified, so generating a hard bounce isn’t as easy as it might seem.

Additionally, in or out of the sandbox, if you send too many emails that bounce, your bounce rate will increase and your email sending will be at risk of suspension due to too many bounces. You might also be concerned about hitting your sending quota (the maximum number of emails you can send in a 24-hour period).

Mailbox Simulator Benefits

  • With these challenges in mind, we designed the Mailbox Simulator so that it:
  • Does not affect your email deliverability metrics for bounces and complaints.
  • Does not count toward your sending quota.
  • Can generate a bounce without putting a valid email address on the blacklist.
  • Can be used in the sandbox. In the sandbox, you normally have to verify recipient addresses. For the Mailbox Simulator email addresses, you don’t have to do that.
  • Can notify you of bounces, complaints, and OOTO responses by using either of the feedback mechanisms provided by SES: by email or by Amazon Simple Notification Service (Amazon SNS) notifications.

Note that when you use the Mailbox Simulator, you are still limited by your maximum sending rate (the maximum number of emails you can send per second).

When to Use the Mailbox Simulator

Here are just a few ideas for when you might want to use the Mailbox Simulator:

  • You just signed up for SES, are in the sandbox, and want to experiment with sending emails and receiving feedback notifications.
  • You are designing your email sending application and want to review typical responses as you consider how your application should handle certain types of feedback.
  • You finished your email sending application and want to trigger bounces and complaints in a controlled fashion to verify that your application handles them as you intended.
  • You finished your email sending application and want to perform scalability testing.

No doubt you will think of other possibilities as you design and test your application.


To read more about the Mailbox Simulator, see the Amazon SES Developer Guide. We hope that you are as excited about it as we are. Please let us know your thoughts by commenting here on the blog, in the customer forum, or on  Twitter.