Extended features stand out

Each product tested offers features beyond basic e-mail. For example, Zimbra Collaboration Suite and MDaemon both have integrated instant messaging servers, and MailSite Fusion has a short message service gateway. But we honed in on specific-business features: webmail, antispam and antivirus support, and unified communications tools because those are the types of tools shipped with Exchange.

All included at least one webmail interface. CommuniGate Pro and Zimbra Collaboration Suite both stood out as having especially snazzy clients, with Scalix Enterprise Edition and Kerio MailServer showing nearly as nice. This doesn't mean that MailSite Fusion and MDaemon had poor webmail interfaces; just that they didn't impress us quite as much.

While you can find fault with any end-user focused Web interface, it's likely that most users would find the webmail tools in these products very satisfactory and easy to use. MDaemon's webmail client was the only one that gave us any significant pause, because there are actually two completely different interfaces -- one in which you complete normal e-mail, contact, and calendar operations and a different one for changing settings. This dichotomy could trip up users who don't understand why the client is suddenly popping up a second window with different colors because they want to set up their vacation message.

Several of the mail servers also had legacy webmail clients built-in, presumably to handle older browsers. Beware, however, of MailSite Fusion's older client: it doesn't actually handle some features properly. Calendaring is what we tripped over. If, for example, you make an appointment using the old webmail client, it won't show up properly in either the other webmail client or in an Outlook client.

Kerio MailServer also offered a stripped-down client specifically geared for mobile devices, while MailSite Fusion had a WAP client for mobile phones. Zimbra Collaboration Suite includes an iPhone-specific client which is especially snazzy, although if you're synchronizing your mail, contacts and calendar using its mobility features, the iPhone client isn't all that useful because you've already got a higher level of synchronization in place via ActiveSync.

With Exchange 2007 built-in support for unified communications services, especially IP telephony, we expected to find similar features in most of these products. But our expectations were misguided. Only CommuniGate Pro includes any significant voice features. Actually, CommuniGate Pro includes a full-on SIP PBX with features such as automated attendant and voice mail (of course), all nicely integrated with the e-mail server. We didn't test the Session Initiation Protocol features extensively because no other mail server included them. However, if you're interested in VoIP integration in CommuniGate Pro, beware: the overall management interface is not for the faint of heart.

While most businesses, even small ones, will want an offboard e-mail security gateway with antispam and antivirus features to gain the highest levels of protection, all of these products have the option to run internal antispam and antivirus as well.