If you are sending your Flyer by email directly through Paperless Post, you will have the option to customize the email's Sender Name and Subject Line before sending.
From your Flyer's Manage Page, select the 'Invite by Email' button. At the top of the page, you will see the editable 'From' and 'Subject' Fields. These will be pre-populated with the Host Name and Event Name that you already set up on your Flyer Details, but can be changed to whatever you would like to show in your recipient inboxes. The Sender Name is limited to 20 characters and the Subject Name is limited to 70 characters: