Conflict in Mail From configuration between SES and Work Mail Results in "MX Record not found in DNS" on SES side

Question

After using SES for over 10 years with no problems, I'm encountering a conflict with the Mail From setup  after migrating Outlook/Exchange online  toWork Mail for the domain. 
Specifically, from what I can see, this involves the MX setup for Work Mail if  a Mail From domain is in use,   creating  two separate MX records, both with a priority of 10. 
One is for inbound mail, with a value of  "inbound-smtp.us-east-1.amazonaws.com." , the other for Mail From, mail.*mydomain*.com with a value of 
10 "feedback-smtp.us-east-1.amazonses.com."

Meanwhile, the documentation for SES specifies that only one MX record is permitted if a custom Mail From domain is used, which is set to   the "feedback..." value, and for some reason, when Work Mail is also in use, SES reports being unable to find any MX records for the pre-existing SES :
"Amazon SES has detected that the MX record required to use mail.mydomain.com as a custom Mail From domain for verified identity mydomain.com in AWS region US East (N. Virginia) is no longer present in your DNS settings." BTW, the DNS is on Route 53

In this case, I would guess that the only way to avoid the MX DNS error in SES would be to not use a custom Mail From domain in either SES or Work Mail, or is there a way to have entries for both in a single MX record.

re:Post Agent · Answer

The issue you're experiencing stems from a fundamental misunderstanding about how MX records work in DNS and how AWS services use them.

First, it's important to clarify that MX records are domain-specific. When you have different subdomains (like mail.mydomain.com vs. mydomain.com), each needs its own separate MX record. These don't conflict with each other because they're for different domains.

For your WorkMail setup, you need an MX record for your main domain (mydomain.com) pointing to:
10 inbound-smtp.us-east-1.amazonaws.com.

For your SES custom MAIL FROM domain (mail.mydomain.com), you need a separate MX record pointing to:
10 feedback-smtp.us-east-1.amazonses.com.

These two MX records serve different purposes and don't conflict with each other because they're for different domains. The WorkMail MX record determines where incoming email for your domain is delivered, while the SES MAIL FROM MX record is used for bounce handling.

When SES reports that it can't find the MX record for your custom MAIL FROM domain, it's specifically looking for an MX record for mail.mydomain.com (not mydomain.com). Make sure this record exists and points to the feedback-smtp endpoint.

If you've verified that the MX record for mail.mydomain.com exists and is correctly configured but SES still reports an error, you might need to wait for DNS propagation (though this typically shouldn't take more than 48 hours). Alternatively, you could try setting up the custom MAIL FROM domain again in the SES console to trigger a fresh verification of your DNS records.

If the issue persists, check the status of your MAIL FROM domain in SES. It might be in a FAILED or TEMPORARY_FAILURE state, which would explain why you're receiving the error message.  
**Sources**  
[How to configure two different email servers (MX)? | AWS re:Post](https://repost.aws/questions/QUNJBxiY0WRfKol-csRytJ7A/how-to-configure-two-different-email-servers-mx)  
[Custom MAIL FROM domain setup – SPF record not recognized despite correct DNS settings | AWS re:Post](https://repost.aws/questions/QUCFyRq18sQdCWmJHLK_z2kg/custom-mail-from-domain-setup-spf-record-not-recognized-despite-correct-dns-settings)  
[One Organization in Workmail not able to send or receive | AWS re:Post](https://repost.aws/questions/QU_cLl7s87Q9Gi7naGF8vxlg/one-organization-in-workmail-not-able-to-send-or-receive)  
[MailFromAttributes - Amazon Simple Email Service](https://docs.aws.amazon.com/ses/latest/APIReference-V2/API_MailFromAttributes.html)  
[PutEmailIdentityMailFromAttributes - Amazon Simple Email Service](https://docs.aws.amazon.com/ses/latest/APIReference-V2/API_PutEmailIdentityMailFromAttributes.html)

Conflict in Mail From configuration between SES and Work Mail Results in "MX Record not found in DNS" on SES side

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