Steps

1. Verify your domain in Amazon SES
2. Register DKIM records (CNAME records) in GCP Cloud DNS
3. Register MX records in Cloud DNS (pointing to inbound-smtp.ap-northeast-1.amazonaws.com.)
4. Create an S3 bucket and configure the bucket policy
5. Create a receipt rule set and rule in Amazon SES in the Tokyo region
6. Send a test email (to the hostname registered in the MX record, e.g.: admin@hostname)

References

https://blog.denet.co.jp/receiving-email-by-amazon-ses/?doing_wp_cron=1727039061.0858280658721923828125#Amazon_SES%E3%81%AEID%E3%82%92%E4%BD%9C%E6%88%90