Email Engagement

Sends an email for the engagement using the tenant's email settings.

The email will be sent to the recipient specified in the engagement.
The email will be queued for sending and a message ID will be returned.
A record will be created linking the engagement to the sent email.

The body is optional. It carries per-send choices made on the send screen — currently which
sales pipeline (if any) to add the client to, overriding Proposal Settings for this send only.