Anti-VirusFor Anti-Virus they seem to run messages through multiple commercial anti-virus scanners on their servers. Messages that trigger positive are quarantined, and a notification will be sent to the site admin and/or the intended recipient of the message notifying them of what happened.
The site admin can report false positives to the vendor who will investigate and release a message if they can confirm that it was in fact a false positive. They also take an action to reduce future false positives based on what they find. These investigations tend to take 24 hours or so.
Anti-SpamSpam tends to be a bit more subjective, so false positives tend to be higher than with Viruses. Due to this, their anti-spam offering makes it a lot easier to both prevent and deal with these situations.
Spam messages can either be tagged for users to filter on their own, or they can be actively filtered and put into a quarantine on their servers. Unlike quarantined virus mail, quarantined spam can be accessed and released by users directly.
In order to prevent false positives site admins are able to whitelist domains, e-mail addresses or IP addresses for specific mail relays. Whitelisting a domain is typically not a great idea in these days of e-mail address spoofing, but e-mail address and whitelisting relays works fairly well.
Where it falls apartSounds good so far, right?
Well, here's where it all goes wrong. It appears that anti-virus vendors have discovered that they can use their scanning engines to pick up certain types of phishing and scam e-mails, essentially adding anti-spam into their anti-virus product.
A phishing or a scam mail is SPAM, not a VIRUS. The difference here cause a big problem when you get spam levels of false positives while removing the user's ability to release their own messages and the site admin's ability to implement an sort of whitelisting.
That's when you start getting end user reports of mail threads with customers going missing. Add in a 24 hour turn around time for releasing the messages when the problem is discovered and you start to consider deep-sixing your vendor.