What are some alternatives?
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
Campaigner - Is your email marketing failing to produce the revenue you expect? Learn how to send email campaigns that deliver results with Campaigner. Try our free 30-day trial today.
Mailwasher - Over 8 million people use MailWasher as their spam filter
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.
Scrollout F1 - Scrollout is a free and easy to use anti-spam email gateway designed for Linux & Windows administrators without advanced email security experience.
Zoho Campaigns - Zoho Campaigns is an email marketing tool with CRM & social media integration to help you create, send and track effective email campaigns.