Horde IMP

Web · Android · iPhone · Self-hosted

Freedom report

Two barsScore 5.6

Free tierA free tier is on its own pricing page
Runs widely3 of 6 device platforms
DocumentedThinly documented

Horde IMP is ranked #95 of 143 in email clients on Freedom251. It runs on Android, iOS, Self-hosted, Web. There is a free plan.

Horde IMP plans and pricing

All plans

IMP Free Open source webmail application; requires a Horde installation and an IMAP or POP3 server horde.org · 12 Oct 2026

Compared on email clients

Free plan: Yes
App coverage: web
Calendar tools: Yes

Best Horde IMP alternatives

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The record

Purpose: IMP is a PHP webmail client that provides browser access to IMAP and POP3 accounts.
Browser views: It provides dynamic, mobile, basic, and minimal text-only interfaces for different browsers and devices.
Composition: Features include HTML composition with a cross-browser WYSIWYG editor, HTML signatures, and drag-and-drop attachment support.
Mail tools: Features include flexible message search, address autocompletion, spell checking, thread view, mailbox previews, and forwarding multiple messages at once.
Mailbox management: It supports IMAP folders, shared-folder ACL management, folder subscriptions, multiple identities, and mailbox quotas.
Integrations: The feature list names integration with Horde's Ingo email filtering, Turba address book, and Kronolith calendar applications.
Encryption: IMP supports S/MIME and PGP-based encryption and signatures; OpenSSL is required for S/MIME and for TLS or SSL connections to mail servers.
Security configuration: The installation guide recommends SSL for browser-to-web-server traffic and TLS or a private network for web-server-to-mail-server traffic; TLS is the default mail-server connection configuration described there.
Prerequisites: IMP requires a working Horde installation, PHP file-upload support, at least one IMAP or POP3 server, and Sendmail or an SMTP server.
POP3 limit: With POP3, on-demand filtering, searching, and sorting are disabled, and the POP server must support UIDL.
Installation: The guide recommends installation through PEAR and also documents installation from Git for development code or unreleased fixes.
Support: The project points users to its FAQ, application mailing lists, and occasional IRC support from Horde developers, contributors, and users.
Open source: The project describes IMP as OSI Certified Open Source Software.
Price from: Free

Where it ranks on Freedom251

Best Email Clients in 2026#95 of 143

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Sources

horde.org/apps/imp/· checked 12 Oct 2026
horde.org/apps/imp/docs/README· checked 12 Oct 2026
horde.org/apps/imp/docs/INSTALL· checked 12 Oct 2026