I had this same issue for the longest time. The solution I found was to go into your Send Forms Preferences (Edit >> Preferences >> Send Forms) and make sure that the "Web Mail" radio button is selected. Then use the "Add" button to select your email provider and input your Email ID and credentials. This then changes the origin email address to your email, and updates the subject line to something like "Subject: Invoice 26564 from [Your Company Name]". Hope this helps!