We're using the Outlook plugin to add relevant emails to Deals.

I'd like to write a Workflow that triggers when an email is added to the Deal, allowing me to update a specific Deal field as a result.

But there's no Field Update trigger for Emails within Deal workflow.

Neither can I trigger based on Email workflow as that only allows me to trigger based on the email message itself (and so I can't update the Deal record that it's attached too). Plus, I'd guess that it only triggers if Zoho is actually receiving the email rather than it being added.

How can I do this?