How to test email sending and monitoring

Introduction

When setting up your email sending infrastructure and connections to APIs it is necessary to ensure proper setup. It is also important to ensure that after making changes to your sending pipeline that you verify that your application is working as expected. Not only is it important to test your sending processes, but it’s also important to test your monitoring to ensure that sending event tracking is working as intended. A common pitfall for email senders is that when they attempt to test their email sending infrastructure or event monitoring they send to invalid addresses and/or test accounts that generate no, or negative, reputation as a result of these sends.

The Amazon Simple Email Service (SES) provides you with an easy-to-use mechanism to accomplish these tests. Amazon SES offers the mailbox simulator feature which enables a sender the ability to test different sending events to ensure your service is working as expected. Using the mailbox simulator you can test: delivery success, bounces, complaints, automated responses (like out of office messages), and when a recipient address is on the suppression list.

In this blog we will outline some information about the mailbox simulator and how to interact with the feature to test your email sending services.

What is the mailbox simulator?

The mailbox simulator is a feature offered to help Amazon SES senders test their sending services to verify normal operation. It provides mechanisms to test their monitoring and event notification services. This feature gives a sender the ability to test their service and email monitoring to verify that it is working as expected without the risk of negatively impacting their sending reputation. The mailbox simulator is an MTA operated by SES that is set to receive mail and to simulate different sending events based on the recipient address used.

Why use the mailbox simulator?

The mailbox simulator provides an easy-to-use mechanism to test your integration with Amazon SES. This gives senders the ability to test their sending environment without triggering actual bounces or complaints, which negatively impact their account sending reputation, as well as not counting against a sender’s email sending quotas.  It is important to test these events to ensure that event monitoring is properly setup and function. A gap in monitoring these events could lead to a decrease in sender reputation from bounces or complaint events going unnoticed. The mailbox simulator gives a sender the ability to programmatically evaluate whether their event monitoring process has been set up properly without the negative impact to their sending reputation that would occur if sending test emails to differing mailbox providers or invalid email addresses.

How do I use the mailbox simulator?

Your first step is setting up a destination for your event notifications. This can be done using Amazon Simple Notification Service (SNS) or by using event publishing depending on your use-case.  Once you have set up an event destination and configured it for your sending identity (either an email address or domain) you are ready to proceed to testing the configuration.

Using the Amazon SES mailbox simulator is simple. In practice, you will be sending an email to an Amazon SES owned mailbox. This mailbox will respond based on the event-type you want to test. Below is a map of the event types and the corresponding email addresses to test the events:

If you are using the Amazon SES console to test these events, SES has already included the addresses to simplify the testing experience and you can find these under the ‘Scenario’ dropdown.

After sending an email to one of the five destinations, you should soon receive a notification, or event, to your publishing destination. This is an example of a success event.

{
    "notificationType": "Delivery",
    "mail": {
        "timestamp": "2023-05-05T21:00:23.244Z",
        "source": "dustin@example.com",
        "sourceArn": "arn:aws:ses:us-west-2:012345678910:identity/example.com",
        "sourceIp": "192.168.0.1",
        "callerIdentity": "root",
        "sendingAccountId": "012345678910",
        "messageId": "01010187edb7434c-4187f4b8-3e2b-404c-a5f6-72b9b64e5d66-000000",
        "destination": ["success@simulator.amazonses.com"]
    },
    "delivery": {
        "timestamp": "2023-05-05T21:00:24.300Z",
        "processingTimeMillis": 1056,
        "recipients": ["success@simulator.amazonses.com"],
        "smtpResponse": "250 2.6.0 Message received",
        "remoteMtaIp": "54.165.247.113",
        "reportingMTA": "a62-102.smtp-out.us-west-2.amazonses.com"
    }
}

If you have not received confirmation of the event, it is likely there is a problem with your monitoring configuration. We recommend reviewing the documentation on SNS topic setup and/or event publishing to uncover if an error was made during initial setup.

Note: A sender may have verified an email address and a domain to use for testing. The domain may have the appropriate configuration while the email address does not. When sending an email from SES, SES will use the most specific identity (email address is used before the domain) and will use the configuration associated with that identity. This means that in this instance you can either remove the email address verification for that domain and re-test or set up the same configuration for that email address that is verified.

What next?

Now that your initial setup of event publishing is complete and you have tested your first event through the mailbox simulator, it is time to set up automated testing using the mailbox simulator. Testing email events after a successful update to your application is recommended to confirm that updates have not caused bugs in your event ingestion mechanisms.

Happy sending!