For secure email
With the regify client for windows you can create, open and read regify messages. It includes an Add-In for Microsoft Outlook (version 2013 and higher). This setup is also needed for Lotus Notes. It is compatible with Windows 10 or newer.
Download regimail Client for Mac
Info about regimail Client for Linux deb
Download regimail Client for Android
Download regimail Client for Ios
Download regimail Client for Thunderbird