Lack of vendor lock-in is an obvious advantage offered by all three of the products we reviewed, but it is not the only one. You can read more comments from von Kurnatowki here.
Back in August, Open-Xchange Executive Vice President of Marketing Strategy Dan Kusnetzky told us that there is plenty of opportunity selling to companies that started as one-person or two-person businesses, with the founders using Hotmail or AOL or Yahoo! or other personal email addresses, but have now grown to the point where they have no choice but to centralize their messaging and start thinking about things like shared calendars, shared documents, and other collaboration features. Kusnetzky had many other interesting things to say about the non-Exchange messaging server market, too.
Scott Dietzen, president and CTO of Zimbra, told Joe 'Zonker' Brockmeier that Zimbra is being used for high-end deployments with companies like H&R Block, Voxel dot Net, San Mateo Regional Networks, and a number of others, and can handle million-user deployments for hosted service providers -- presumably at a much lower cost than an equivalent Microsoft Exchange setup. Dietzen, too, had lots more to say.
In a comment, an anonymous reader asked, "Why is there so much rumor about OpenXChange, Zimbra, Scalix and other bad Groupwares?" This reader also said, "eGroupware leaves them all behind and is REAL Open Source, but nobody writes reviews about it. Go and take a test drive!"
The last time we looked at eGroupware we decided it wasn't quite ready for full-scale enterprise use and that we'd be doing its developers no favor by reviewing a project that still needed a lot of work to be useful. That was several years ago, and the project has come a long way since then. Look for an eGroupWare review on Linux.com before long.
While none of the products we've reviewed in the last week -- or eGroupWare -- seem to be direct replacements for Microsoft Exchange in that they duplicate each and every Exchange feature, they all have their good points, and since they are all offering (or plan to offer) "plug and go" server appliances, installation and maintenance worries should not be the main reason for choosing or not choosing one of them. All three seem to be building their user bases steadily, if not as rapidly as they'd like, so it's obvious that there is at least a noticeable market niche for new messaging server products -- especially if they run on Linux, which Microsoft Exchange does not and probably never will do.
If you know of any other Exchange-like products or projects we haven't mentioned recently, please let us know about them. Also note: This "special report" format, where we do intense coverage of a particular software or hardware niche in a single week, is as new to us as it is to you, and we would love to have your advice on how we can do it better, either posted as a comment below or by email sent to firstname.lastname@example.org.