Mailvelope is available as a web browser extension for Chrome / Chromium and Firefox. It uses OpenPGP.js to add encryption and digital signature capability to any webmail service.

Enigmail is a seamlessly integrated security add-on for Mozilla Thunderbird. It allows you to use OpenPGP to encrypt and digitally sign your emails and to decrypt and verify messages you receive.

Enigmail is free software. It can be freely used, modified and distributed under the terms of the Mozilla Public License.

privacytools.io provides knowledge and tools to protect your privacy against global mass surveillance.

IMAPFilter is a mail filtering utility. It connects to remote mail servers using the Internet Message Access Protocol (IMAP), sends searching queries to the server and processes mailboxes based on the results. It can be used to delete, copy, move, flag, etc. messages residing in mailboxes at the same or different mail servers. The 4rev1 and 4 versions of the IMAP protocol are supported.

IMAPFilter uses the Lua programming language as a configuration and extension language.

On this page, you will find a listing of various email service providers with specific information around security and privacy.

Kaiten is an excellent email client for Android phones and tablets.

Kaiten Mail is an advanced email client for Android. Based on the award-winning K-9, Kaiten has been completely redesigned to look gorgeous on your tablet. (It looks pretty snazzy on your phone too.)

Kaiten supports IMAP Push, POP3, Exchange 2003/2007 (with WebDAV).

Kaiten supports multi-folder sync, flagging, filing, signatures, bcc-self, PGP, mail on SD, multiple identities, search, configurable notifications & more!

Built by K-9's lead developer, Kaiten is simpler, easier to work with and a whole lot prettier. Frequently used commands are now available in the application's action bar. If you have the screen real-estate, Kaiten's split-screen view lets you see a mailbox and individual messages side-by-side.

If you're having trouble with Kaiten, drop me a line and I'll do everything I can to help you out.

Please note that neither K-9 nor Kaiten Mail currently support Exchange ActiveSync.

Kaiten's name is a play on K-9. It's a Japanese word that means rotation and sounds a lot like K10 or K-10.