Best in the industry IMO, Symantec did go through a bit of a bad patch a few years ago but their AV has picked up every single threat we've encountered on servers and our corporate network over the past two years without a single infection - that's a pretty good track record.
Firewall wise, I've used many different options, and none of them have the number of features, or the clever bits that Kerio does.
█ Dan Kitchen | Technical Director | Razorblue
█ ddi: (+44) (0)1748 900 680 | e: [email protected]
█ UK Intensive Managed Hosting, Clusters and Colocation.
█ HP Servers, Cisco/Juniper Powered BGP Network (AS15692).
For anti virus, I have used McAfee now for a few years have no complaints.
For a more affordable mail server solution for virus and spam, I'm looking into @Mail email server. They come with open source modules by default, spamassassin and clam for the anti-virus but you can swap for other commercial ones. It also works on any platform.