Outlook Mail Format View The Full Article There are several mail formats available for composing messages in Outlook. Some mail clients e.g. Eudora have issues with receiving mail in formats other than Plain Text. If you know you are sending mail to someone using Eudora or if you receive feedback from a recipient about problems with the mail format, you should send messages in Plain Text. If you want to send a message in a format other than your default mail format, you can click the Options ribbon and select Plain Text, HTML or Rich Text. For more information about mail formats, type mail format in the Ask a Question box.