Manual emails are populated by the profile information.
However that same email is also used by GHL for login and notifications so it has to be an external email /domain.
This creates a problem when a users send a manual email they have to change the email EVERY time or it will go into spam as it sends the email on behalf of.
I would request 1 of the following solutions
1) Add a second email field on the profile called system email and have manual emails pull from there. so we set their email to be the proper name and domain.
2) default the email as {{user.firstname}}@privatedomain.com where the domain is set by the email system.