What are some alternatives?
SpamTitan by TitanHQ - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.
Symantec Email Security.cloud - Symantec Email Security.cloud provides always-on, inbound and outbound email security against malware, targeted attacks, and advanced threats
MailArchiva - MailArchiva is an email archiving, email compliance, and ediscovery enterprise software server.
Barracuda Essentials for Email Security - Barracuda Essentials for Email Security is an easy-to-use cloud-based email security service.
SpamTitan - SpamTitan is an anti-spam email solution specifically developed to meet the demands of modern business. Delivering a spam detection rate over 99.9%
dmarcian - Safeguard your email from abuse