Today, Amazon WorkMail announced that you can access full email message content from within your AWS Lambda functions when using Email Flow Rules. With this, you can build powerful email processing, automation, and analytics applications; for example, you can easily add email correspondence to a 3rd party productivity tool such as SalesForce or Asana whenever an email is received, or analyze your organization’s email traffic to spot trends. Email messages can be accessed on both incoming and outgoing email.  

from Recent Announcements https://aws.amazon.com/about-aws/whats-new/2019/09/workmail-message-flow-sdk/