What are some alternatives?
Mailwasher - Over 8 million people use MailWasher as their spam filter
Hornetsecurity - Hornetsecurity offers you comprehensive, integrated managed e-mail security services.
Spamfence.net - Professional e-mail security free for private use: With Spamfence.
Symantec Email Security.cloud - Symantec Email Security.cloud provides always-on, inbound and outbound email security against malware, targeted attacks, and advanced threats
Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.
dmarcian - Safeguard your email from abuse