Upgrade to 4.0.
The major changes compared to the IMP 3.x versions are:
* Much improved message format support through Horde's rewritten MIME
* 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.
This is a resurrection of the previous mail/imp, upgraded from mail/imp3.
Submitted by: /me