Writing to the EmailMessage Object
When to use this guide: Use this guide when configuring or validating CRM integration behavior.
One question that has come up related to the EmailMessage object is, “Is it possible to change the Status field to be Read instead of Sent?”
Unfortunately, no. For emails not sent as part of a case, only the status Sent is valid.
However, OutboundSync does have the ability to write activities to the Task Object with a configurable subject line. That could include the EVENT_TYPE (in this case EMAIL_REPLY).
For more information, read the EmailMessage section of Salesforce’s documentation.