Unable to access account (email code cannot be delivered)

I understand you're in a difficult situation with your AWS root account access. This is a known issue when your email domain is hosted on the same AWS account you're trying to access.

Since you can't receive the email verification code because your domain's DNS is managed in Route 53 on the same account (with apparently missing MX records), you'll need to contact AWS Support directly. This is the recommended approach when you can't receive verification codes due to DNS configuration issues with your email domain.

For account access issues like this, you can contact AWS Support even without a support plan. When contacting support, be prepared to verify your identity as the rightful account owner. You'll likely need to provide information such as:

• The email address associated with the account
• The AWS account ID
• Billing information
• Other identifying details about your AWS resources

Regarding your concern about the account possibly being compromised due to missing MX records, this is something AWS Support can help investigate once you regain access. The change in login behavior (now requiring an email code when it didn't before) could be due to security settings changes or AWS implementing additional security measures.

This is considered an urgent account access issue, and AWS Support typically treats these with high priority, especially when it impacts business operations.
Sources
sign in issue into my root account because the email is on aws DNS | AWS re:Post
Urgent: Root User MFA Issues - Cannot Access AWS Account Due to Invalid Contact Methods | AWS re:Post