Even as social networking continues to gain in popularity, email remains the undisputed workhorse of messaging, far eclipsing all other forms of electronic communication. Email administration can be a costly function, especially for small to midsized organizations, and many administrators are looking for alternatives to enterprise-sized (and priced) commercial products.
For this review we tested six free or open source email server products: Apache James, Citadel, hMailServer, SmarterMail, Zarafa and Axigen. Most have commercial options, but we specifically limited our testing to the free or community editions. Some, like Zarafa and Axigen, can also scale to handle large volumes of users, while SmarterMail and Citadel are more suitable for small to midsized organizations.
The six products we chose fall into three categories: Linux-only, cross-platform and Windows only. Our Linux-only contenders are Citadel, an open source product with roots back to the early 1980s and Zarafa, a European product with several features to support mobile mail.