具有免费许可证的OpenPGP版Nylas Mail Lives的替代品

• OpenPGP
  所有平台 Windows Mac Linux Chrome OS Android iPhone Apple Watch iPad Android Tablet Web Self-Hosted BSD Haiku PortableApps.com Slack F-Droid Ubuntu Ruby Gmail GNOME Arch Linux Fedora Cloudron Amazon Echo (Alexa Voice Service) OpenPGP PureOS (Purism) S/MIME
• 免费许可证
  任何牌照 免费许可证 开源许可证 商业牌照