Emails not receiving in workmail, but able to sent

This is a common issue with Amazon WorkMail and there are several potential causes and solutions to explore:

1. Check your MX (Mail Exchanger) record: Ensure that the MX record for your domain is correctly pointing to WorkMail and that it's the only entry with the lowest priority. Multiple MX records can cause emails to be routed to the wrong service.

2. Verify DMARC (Domain-based Message Authentication, Reporting, and Conformance) settings: Review your DMARC settings in the Amazon WorkMail console. Incorrect DMARC configuration can affect email delivery.

3. Examine Amazon SES (Simple Email Service) inbound rules: WorkMail uses SES for email routing. Check if there are any SES inbound rules that might be interfering with email delivery to your WorkMail organization.

4. Enable message tracking: Turn on email event logging in WorkMail to help identify any delivery issues.

5. Confirm domain permissions: Ensure that WorkMail still has the necessary permissions to use your domain. If permissions have changed, you may need to add the domain again in the WorkMail console.

6. Check for missing records: Verify that all required DNS records are present, including DKIM and custom Mail From domain records. These are important for proper email delivery.

7. Review SES recipient rules: Make sure the SES recipient rule that directs mail to your WorkMail organization is still in place. If it's missing, you may need to add your domain to WorkMail again to recreate this rule.

If these steps don't resolve the issue, you may want to contact AWS support for further assistance, as there could be account-specific factors affecting your email reception.
Sources
Mail routing - Amazon WorkMail
can't send email to workmail | AWS re:Post
Workmail not receiving mail | AWS re:Post