RE: Show contact email address in email thread when forwarding email
Hi chrisambro123,
Unfortunately, there are no any OOB settings to add original sender email address into email body content (description field).
However, you can create a flow to get original email sender address in forward email, then you can create new field in email to store the address.
Here are steps.
1.Create new field and add it to the email form.

2.Go Power Automate(https://us.flow.microsoft.com/en-us/ ) to create an automated flow.
3.Set trigger.

4.Set condition.
As in my last answer, the forwarded emails will automatically populate the ‘Parent Activity Id’ field.

5.Get record under ‘Yes’ branch.

6.Update a record.

7.Save the flow.
8.Test.
I forward one email (test 2/24), the original sender email address field is null and Parent Activity Id is test 2/24.

Now, the original sender email address can be filled automatically after clicking save button.

Then you can copy original sender email address field value to description field to send the email.
Regards,
Leah Ju
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