Although it's only a couple of months since we reviewed the previous version of Tumbleweed's MailGate anti-spam product, the company has now produced a new release with some significant extra features, so we thought we'd take a look at what's changed.

As before, the device comes as either a 1U appliance (capable of handling 40,000 email messages per hour, according to the spec) or a 2U appliance (which almost doubles the capacity, but more importantly includes essential features such as hot-swappable power supplies).

Since we reviewed the previous version, Tumbleweed has responded to our comment that the Intent Based Filtering didn't do what it said on the tin – namely to spot spam without using "signature files" of naughty words. Although this is what TumbleWeed's IBF white paper led us to think, the reality is that the unit does know naughty words – but it does some work analysing the context in which those words are used before deciding whether something is spam or not. In this context, the system actually does seem to work: we tried the usual plethora of "Viagra" emails, and depending on the context in which they were used, the MailGate made a decent stab at deciding whether something was blatantly spam or not. According to TumbleWeed, the more you use the system, the more it can "learn" about what spam looks like; this is common with heuristic spam filters, which modify their rules when you (for example) tell it "That's not spam" for a message that it has flagged as dodgy.

Because Tumbleweed quite naturally wants to keep the actual algorithms of IBF to itself, it's impossible to say just how good it'll be (natural language semantic processing is a vast, complex subject), but some of the basic examples we used did seem to land in sensible places. Some didn't, of course, but spam identification isn't an exact science.

Enough about IBF – what's new in the latest release? Then there are some modest changes to the admin Web GUI to make the box feel more like a Tumbleweed unit (the device was originally made by Corvigo, which Tumbleweed acquired in the Spring of 2004). The Corvigo name isn't eradicated completely, though – the firmware update URLs still point at the old URL, for instance. Also new in 2.2. is the Dynamic Anti-Spam service – another heuristic tool that updates its engine via the Internet several times a day to learn about new spam techniques.

MailGate 2.2 is a reasonably attractive anti-spam product that is trying to stand out from the crowd by using Tumbleweed's proprietary IBF analysis engine. It remains to be seen whether the inclusion of the proprietary IBF technology is sufficient for people to choose this product over one of the many competitors in the market, but to be fair to Tumbleweed, at least they've tried to make something that doesn't just tick all the same boxes that the others tick. On the downside, the client GUI is still pretty basic – it's a long way off the standard of the average WebMail interface, and some of the competition goes as far as having Outlook plug-ins and whatnot that let you interface with the anti-spam appliance from the Windows desktop.

In short, then: a useful box that tries to do something different in IBF, but which we still think isn't, in every aspect of its design, as refined as some of the competitors – particularly BorderWare's MXtreme.


Although more expensive, the 2U unit is more fault-proof, as it has redundant PSUs.