MX Save - MXSAVE is an email disaster recovery service that works seamlessly with on-premise or hosted anti-spam solutions.
dmarcian - Safeguard your email from abuse
Happy Moose - Happy Moose is a super-efficient cloud anti-SPAM solution for organizations. It stops up to 99.
Proofpoint - Proofpoint provides cloud-based email security, e-discovery and compliance solutions for companies to protect sensitive business data.
SMXemail - SMX – Cloud-Based Email Security.
Barracuda Email Protection - Barracuda Essentials offers advanced Office 365 security features including email scanning, archiving, backup & recovery, and real-time phishing defense.