SES Mail Manager forwarding one email address

It seems like you're experiencing an issue with your SES Mail Manager setup for forwarding emails to your helpdesk. Let's break down the problem and suggest some potential solutions:

1. MX Record: Your MX record is correctly set to "inbound-smtp.us-east-2.amazonaws.com", which is a good start.

2. Bounced Emails: The error message "550 5.1.1 Requested action not taken: mailbox unavailable" typically indicates that the recipient's email address is not recognized or the mailbox doesn't exist. This could mean that SES is not properly configured to handle the incoming email for your helpdesk address.

3. EC2 and Postfix: Your plan to use an EC2 instance with Postfix for forwarding is a valid approach, but it seems the emails are not reaching this stage yet.

4. Mail Manager Dashboard: The fact that the dashboard shows 0 rejected emails suggests that the emails might not be reaching SES at all, or there might be an issue with how the rules are set up.

To resolve this issue, consider the following steps:

1. Verify Domain: Ensure that your domain is properly verified in SES.

2. Rule Set Configuration: Check if you have properly configured a rule set in Mail Manager to handle incoming emails for your helpdesk address. You should have a rule that specifies what to do with emails sent to helpdesk@yourdomain.com.

3. SMTP Relay: If you want to use your EC2 instance as an intermediary, you can set up an SMTP Relay in Mail Manager. This would allow you to route incoming emails to your EC2 instance for further processing.

4. Ingress Endpoint: Make sure you have set up an Ingress Endpoint in Mail Manager and that it's properly linked to your rule set.

5. Permissions: Verify that SES has the necessary permissions to handle incoming email for your domain.

6. Testing: Try sending a test email directly to the SES SMTP endpoint to see if it's received and processed correctly.

If after checking these points you're still experiencing issues, you may need to review your Mail Manager configuration in detail or contact AWS support for further assistance. Remember that Mail Manager is designed to simplify email workflow management, so once properly configured, it should handle this forwarding scenario efficiently.
Sources
Mail Manager – Amazon SES introduces new email routing and archiving features | AWS Messaging & Targeting Blog
How to use SES Mail Manager SMTP Relay action to deliver inbound email to Google Workspace and Microsoft 365 | AWS Messaging & Targeting Blog