Retrieves the message text of messages specified by the MessageSet property.
public func fetchMessageText() throws -> Void
This method retrieves the RFC822-encoded text of the message specified by MessageSet. If the LocalFile property contains a file name, the text is stored in LocalFile, and the Transfer events denote the progress. If the LocalFile property contains an empty string, the text is stored in the MessageText property, as well as provided through the Transfer event.