The email component offers a variety of filtering that includes anti-virus and anti-spam. The documentation makes grand claims about the possibility of 100 percent spam blocking. The product falls well short of that, but it can be tuned to perform reasonably well for a combined solution that is trying to do so many things at once.
Configuration, like nearly everything else about the system, is via a web browser. A few components rely on separate applications and even a command line tool (to set up a certificate for SSL), but most of it is intuitive and well-presented.
Most components of the system are either extremely easy to manage or oddly complicated. Gordano seems to have put an enormous amount of work into features most users would want and hiding those few would demand. This applies to a number of areas – the system is far more flexible than it first appears. Fortunately, the documentation is good and makes it easy to find the right options.
Anti-spam facilities include RBL (on by default, but with no servers configured), RDNS (off), and a clutch of rate-limits to stop mailbombs and dictionary attacks. The server also tries to bounce failed email back to senders (unwise in the modern spoof-everything era of spam and viruses).
A variety of message quality and RFC-compliance checks round out a thorough set of tests for junk mail.
Strangely, the documentation's recommended defaults do not match those in the base install (all off). Also, the system blocks some junk mail in the SMTP session instead of tagging it, which may worsen the impact of false positives.
Spam blocking was good but not exceptional and under heavy load it slowed the server significantly (not ideal when it is running several services). Realistically, people will buy GMS for the suite (which is very good), not for the anti-spam.