The Horde framework evolved from the IMP (Internet Messaging Project) webmail that Chuck Hagenbuch published on Freshmeat in 1998.

[8] The software has been packaged for all major Linux distributions[9][10][11] and is available as a component in hosting tools such as Plesk[12] or cPanel.

[13] With the release of Horde 4.0 in 2011[14] the framework saw significant architectural changes, a split into nearly a hundred separate PEAR packages[15] and support for smartphones.

One of the tainted packages was picked up by the unstable branches of Debian and Ubuntu and were fixed immediately after the successful attack was disclosed.

[20] This means that Horde can not be run on a modern, supported version of PHP anymore which forces its users to migrate to other webmail/groupware software alternatives.