ProfiMail allows to compose email messages in rich text format, which allows to change text characteristics:
Technically, rich text is converted from/to HTML format when stored in email message. If there are embedded images, the message is also using multi-part mime format for keeping both text and images.
In rare cases, it may be needed that ProfiMail doesn't use rich text format, and sends message as plain text 1). For such cases, the message composer offers option Use plain text, and all possible formatting will be removed prior to sending message 2).