I seem to have crossed some kind of spam tipping point over the weekend, with more spam hitting my Inbox than is being filtered out by two levels of spam filters (one on the server, one on my mail client). There was a time when as much as 90% of the spam was being caught by this two-level approach, but no more. I'm now getting only about 50% of spam trapped by the filters.
Spammers are using two techniques to foil the filters. The first is the relentless use of zombie machines that have been infected to send out email from apparently legitimate source email addresses; they do this so the filters can't "learn" origination email addresses and block them. The second is equally pernicious; they are using increasingly sophisticated phishing techniques to create emails that look exactly like the messages we get routinely from legitimate companies. For example, over the past several weeks, I have apparently ordered at least one thousand large screen TVs from Amazon. The order confirmation message looks EXACTLY like the legitimate order confirmation messages I receive from Amazon. So I can't mark these emails as spam, or the occasional real message will be blocked. I get these phishing emails from US Air, from American Express, from Verizon, from AT&T, and many other companies.
This is a slow motion catastrophe. I would estimate I am now spending as much as 45 to 60 minutes per work day just reviewing and deleting spam from my Inbox. I can typically tell from the subject heading, but it takes me as much as thirty minutes in the morning to delete some 300-600 spams, and then additional time every time I check my email during the day.