HEY - Email at its best, new from Basecamp.
docNCRYPT - docNCRYPT is a cybersecurity platform which only focuses on its core services in protecting your email directly from the different email service provider and allows you to integrate your business email portal in the online service.
InstAddr - Disposable email address application.
LuxSci - LuxSci providing HIPAA-compliant email, secure email & web services.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
encryptomatic - encryptomatic is a smart email encryption software which provides tons of tools in encryption protocols for secure communication and business transaction.