As the text of these messages say, they aren't really email messages. They are created whenever you read your email with a program that uses the IMAP email protocol to handle your Inbox and other email folders. IMAP creates these messages, which it uses for internal record keeping.
You shouldn't see these messages when you read your email with an email program that is set up to use IMAP. That includes WebMail and pine, which use only IMAP. You can also set up Eudora, Netscape, and Outlook to use IMAP rather than POP.