TODO (Feel Free to add information, please indicate if it is Free Software or not and if it uses the recommended ~G~PGME and uiserver ~APIs of ~GnuPG)

=== Enigmail

https://www.enigmail.net

//a data encryption and decryption extension for Interlink Mail, Postbox, and Thunderbird v68 (or older), that provides OpenPGP public key e-mail encryption and signing. //

License: MPL 2, GNU GPL 2+

API: **no ~G~PGME**, **no UIServer**

=== Thunderbird

https://thunderbird.net

Thunderbird v78 supports OpenPGP natively, but can also delegate private key operations to GnuPG (https://wiki.mozilla.org/Thunderbird:OpenPGP:Smartcards)

License: MPL 2 and other free licenses

API: GPGME

=== Mailpile

| https://www.mailpile.is | GNU AGPL & Apache 2 | their own (?) gpgi.py, **no** ~G~PGME, **no** UIServer |  EMail Client, experimental: //Mailpile UI is written using HTML5 and Javascript, running against a self-hosted Python application// |

=== CipherMail Email Encryption Gateway 
http://www.ciphermail.com/gateway.html

License ~GNU +APL 3 (some additional permissions)

Former ~DJIGZO provides a //solution to securing your email without requiring additional client software. The centralized policy based encryption engine can be setup to automatically encrypt email based on regulatory compliance or business rules //

API: **no ~G~PGME**, **no UIServer**. Seems to call gpg directly. 


=== check-trustpaths
https://gitlab.com/jnxx/check-trustpaths


Command-line tool which quickly searches chains of trust signatures from a trusted key to a unverified key (for example a key used to sign software downloads), downloads and refreshes all required keys, and checks all signatures locally using GnuPG. 

The data how keys are connected is retrieved using the (still experimental) PGP pathfinder service. Is supported for example on Debian Jessie, Mint or Ubuntu (only requires gnupg-1.4.18 or gnupg-2.0.26, Python-2.7 and python-gnupg-0.3.6 or newer). Port to Python3 and support for PGME is planned.

| Download: https://gitlab.com/jnxx/check-trustpaths | License: ~GNU GPLv3 | API: **no ~G~PGME**, **no UIServer** | Calls gpg directly|


=== Schleuder, Crypto Mailinglistproduct

| http://schleuder2.nadir.org/ | GNU GPL 2 | TODO | Mailinglist with encryption - Version 2|
| http://https://schleuder.nadir.org/ | GNU GPL 3 | TODO | Mailinglist with encryption - Version 3|


=== gpg4usb

http://www.gpg4usb.org seems to use ~GnuPG 1.4.x and Qt. 

//portable-application, which combines a simple text-editor with a GnuPG-frontend to write, encrypt and decrypt your text-messages and files.//

API: Version 0.3.3 may still use ~G~P~GME. The TODO file aims for the use of its own kgpg connection. **no UIServer**

=== duplicity

//Duplicity backs directories by producing encrypted tar-format volumes and uploading them to a remote or local file server.//
[..] //uses GnuPG to encrypt and/or sign these archives//

License GNU GPL v>=2.

API: uses its own embedded gpginterface.py, process based, **does not use ~G~PGME**

=== ~GoodCrypto

GoodCrypto offers an open source live operating system at https://goodcrypto.com which automatically encrypts and decrypts mail for everyone in a group. The server software runs on your system and integrates GPG into your MTA. GoodCrypto publishes the libraries source at https://gibhub.com/goodcrypto/. Libraries are licensed under GNU GPLv3. The rest of the source is in the ISO. License details are at https://goodcrypto.com/qna/technical/goodcrypto-open-source/. 
API: GoodCrypto calls GnuPG directly (**does not use ~G~PGME**).

=== Confidant Mail

Confidant Mail is an email client and server using GPG encryption and signatures. It is not based on SMTP, but uses a block-oriented protocol which allows unlimited attachment length. It supports Tor and I2P anonymity, and has its own key distribution system. Works with GnuPG 1.4.19 or 2.1.1, does not use GPGME, uses gnupg.py and direct calls to GPG. Windows, Linux, MacOS. GNU GPL.
https://www.confidantmail.org

=== Outlook Privacy Plugin

| http://dejavusecurity.github.io/OutlookPrivacyPlugin/ | BSD |  no ~G~PGME | C# / .NET Plugin for Outlook 2010 and later for PGP using GnuPG (recommending Gpg4win for certificate management) |

=== CypherDocs

CypherDocs keeps your files encrypted while allowing seamless access to read/edit/update those files. Opening any encrypted file (e.g. proposal.docx.gpg) is a just a simple double-click in Windows Explorer. If you edit your document, those changes go back into the encrypted file without any additional effort. Note that you need to close the application used for editing the file (e.g. Microsoft Excel) with before these scripts proceed to check for changes and re-encrypting the file(s).

On a technical level, it's a bunch of PowerShell scripts that glue OpenPGP/GnuGP, Windows Explorer, Windows Applications and Cloud Storage Tools (e.g. Dropbox, OneDrive etc). If you are a developer and want to improve, please feel to collaborate via GitHub pull requests.

| https://github.com/sidshetye/cipherdocs | MIT |  TODO | use GPG and Windows Explorer for a convenient, encrypted Dropbox/OneDrive/Google Drive etc. |

=== JavaCardOS

| http://javacardos.com/wiki/index.php/home/article/detail/category/PC_logon.html | ? | ? | use SmartCard to Login to Windows |