Mautic 7.1 installed with Docker on Ubuntu. Install is about a week old and still in testing. I began receiving support emails from AWS saying DKIM keys were being created. CloudTrail showed that somehow the perpetrator had managed to expose the access key id from the Amazon IAM user. I had left that user with SES full instead of SES send only permissions. My mistake there, but the fact that they could expose the key is a problem.
Agent was Botocore 1.42.66 into AWS once they had the key.