Hornetsecurity VS Barracuda Email Security Service

Proofpoint - Proofpoint provides cloud-based email security, e-discovery and compliance solutions for companies to protect sensitive business data.

Trustwave Secure Email Gateway - Trustwave Secure Email Gateway helps protect your email environment against modern threats such as malware, ransomware and phishing, and helps prevent loss of sensitive corporate data.

Mimecast Gateway - Mimecast Gateway is a SaaS-based email security solution that uses sophisticated, multi-layered detection engines and intelligence to protect email data and employees from malware, spam, advanced threats and zero-day attacks.

Mimecast Secure Email Gateway - Prevent targeted email-borne attacks with Mimecast Secure Email Gateway for cloud-based anti-virus and anti-spam protection.

SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.

Appriver - AppRiver is an email and web security company, develops SaaS-based anti-spam, hosted exchange, email encryption and web protection solutions.