How do recipients choose between text and HTML e-mails?
Messages sent with ListMessenger are sent using multi-part alternative, which means that if the end-user’s e-mail client both supports and has enabled messages to be displayed as HTML; they will be displayed as HTML. If a user’s e-mail client either does not support, they have HTML messages disabled or there is no HTML version of the message present, e-mails sent with ListMessenger will be displayed as plain text.