- For postcards this will specify content for back of postcard.
- For notecards and giftcards this will specify content for the interior of the card.
- For windowed and windowless letters this will specify content for the cover letter.
- The
messagefield can be used to provide the text content directly. - A
message_templateID can be specified to use a pre-designed thanks.io message template. Message templates can have QR Codes and handwriting settings associated with them.