Imp is the internet messaging program (formerly, among other things, the imap webmail program), a php-based webmail system and a component of the horde project. imp, once installed, accesses mail over imap thus requiring little to no special preparations on the server on which mail is stored.

imp offers most of the features users have come to expect from their conventional mail programs, including attachments, spell-check, address books, multiple folders, and multiple-language support.