Amazon SES cannot find DNS Records for "custom MAIL FROM domain" (after some time)

I am setting up an identity on Amazon SES (Simple Email Service) with a "Custom MAIL FROM domain".

After setting the required DNS records, the verification status changes from pending to verified, as expected. So far so good.

But then, usually after ~3 days, I get an email from Amazon saying that the the DNS records for the "Custom MAIL FROM domain" could not be found anymore. And after another day or two, I receive another email saying that "Custom MAIL FROM domain" has been deactivated.

When I go to the console it does indeed show up as "Not configured".

The funny part:

• Those DNS Records were never modified/removed.
• If I dig MX subdomain.domain.com +short and dig TXT subdomain.domain.com +short – both records are still there and contain the right values.

What's the issue with Amazon SES? Am I missing something?

By the way, this will happen for every domain I set up. Every single time. And it always happens after ~3 days.

EDIT: This question IS related to software development. Unless AWS is not related to software development anymore.

You cannot have multiple MX records for the same subdomain. So it seems that it's not possible to use one subdomain for both sending and receiving emails with Amazon SES.

This will not work (at least in the long term¹):

• subdomain.domain.com for sending and receiving emails:
  • MX 10 feedback-smtp.region.amazonses.com
  • MX 10 inbound-smtp.region.amazonaws.com

Instead, you'll need something like:

• out.domain.com for sending emails:
  • MX 10 feedback-smtp.region.amazonses.com
• in.domain.com for receiving emails:
  • MX 10 inbound-smtp.region.amazonaws.com

¹ It will seem to work at first, but after some days it will break, as described in the question.