Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.

Proofpoint Email Security and Protection - Learn about Proofpoint's email security solutions that protect organizations against threats such as email fraud, phishing, spam, bulk email, and viruses.

Roundcube - Web-based IMAP email client

Symantec Email Security.cloud - Symantec Email Security.cloud provides always-on, inbound and outbound email security against malware, targeted attacks, and advanced threats

Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.

Cisco Email Security - Cisco Email Security protects against ransomware, business email compromise, spoofing, and phishing.