IMP is written in PHP and a component of the collaborative software suite Horde.

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 GPL-2.0-only license.

At that time a WAP based mobile view was provided by a separate package called MIMP.

[10] With the release of Horde 4.0 the three existing views were collapsed into the original IMP package again.