The Internet Messaging Program or IMP is a webmail client. It can be used to access e-mail stored on an IMAP server. IMP is written in PHP and a component of the collaborative software suite Horde. It is included with cPanel and Plesk installations as a webmail client. It often integrates email, calendar, address book, notes, tasks, filters and a newsreader with cPanel. Internet Messaging Program is free and open-source software subject to the terms of the GNU General Public License (GPL).