Customers looking for an alternative from the open source community or commercial open source vendors are in luck as there is now a host of choices. On top of standard messaging and collaboration features, many of them bundle a ton of other features and functionality, such as built-in antispam and antivirus, file or document management, cross-platform support (ie can often run on both Windows and Linux) and many others. In this list, I’ll try to list down the well known enterprise-ready alternatives and rate them based on their features, extensibility and adoption.

Low cost CRM packages or services for small and mid-sized business looking to implement CRM in their organization.