IMP H3 (4.0) is now available. This is a major upgrade on top of IMP 3.

The major changes compared to the IMP 3.x versions are:

• Much improved message format support through Horde's rewritten MIME system
• Many, many additional and improved mime viewers for attachments
• Encrypting, signing, decrypting and verifying of signed and encrypted messages (PGP/GPG and S/MIME)
• Message filters moved to a separate application (Ingo) to support more filter backends and a more robust/comprehensive/easy-to-use UI
• Full charset support in folders, mailbox, message and compose views
• Mail folders in the left menu
• Experimental support for virtual folders
• Preview of attachments in compose view
• Send attachments as links
• Option to not save attachments with sent mail
• Navigation through message and mailbox views with arrow keys
• View all messages of a thread
• HTML message composition with a cross-browser WYSIWIG editor
• Fetching mails from other email accounts to view with IMP
• Message previews in mailbox view
• Prevent message loss during compositon due to session timeouts
• Management of shared IMAP folders
• Priority settings for composed messages
• User management for supported IMAP servers
• Integrated quota support
• Support for mailing list headers
• Ability to forward multiple messages at once
• Downloading of all attachments from a message as a single ZIP file
• Stripping individual attachments from messages
• Alias and "tied to" addresses in user identities
• Authentication with Horde credentials
• Graphical emoticons and country flags in message view
• Various caching improvements to drastically minimize duplicate IMAP server->web server traffic

IMP 4.0 requires PHP 4.3.0 or higher, and will operate with version 3.0 of the Horde Application Framework.