Outlook-Privacy-Plugin is described as 'Outlook Privacy Plugin is a security extension for Outlook 2010. It enables Outlook 2010 to send and receive email messages that are encrypted and/or signed with the OpenPGP standard' and is an app in the office & productivity category. There are four alternatives to Outlook-Privacy-Plugin for a variety of platforms, including Windows, Microsoft Office Outlook, OpenPGP, S/MIME and Online / Web-based. The best alternative is GPG4Win, which is both free and Open Source. Other great apps like Outlook-Privacy-Plugin are OneTime, Toolsley PGPigeon and gpg4o.
Gpg4win enables users to securely transport emails and files with the help of encryption and digital signatures. Encryption protects the contents against an unwanted party reading it. Digital signatures make sure that it was not modified and comes from a specific sender.
OneTime is an open source encryption program that uses the one-time pad algorithm to allow two parties to communicate privately. It has features to assist with the bureaucracy of pad management, and comes with built-in help. OneTime requires Python 2.