This is the HTML version of the current message.
If the user wishes to send an HTML entity as a part of the message, it must be set in the MessageHTML property. The HTML must be an entire HTML document, including the <html> and <body> tags.
If TreatMessageAsHTML is set to True, and MessageHTML is not set, the contents of the message will be treated as the HTML entity. If ParseHTML is set to True, the HTML entity will be parsed and its textual contents sent in the <body> element. This behavior will be overridden if any value is found in MessageText.
Note: if the HTML entity does not conform to a strict XML structure (e.g., has unbalanced tags), the XMPP adapter will fail with an error.
This property is not available in the Receiver.