With utmost humility, and respect (and awe) I say unto you... (Microsoft, yahoo and others included)
Today I found 2 mails in my spam folder, that I do not classify as spam - Sure they are promotional mails, but I never said they were spam. This is not the first time this has happened. There have been a couple of times when some critical communications have ended up in my spam folder. I managed to get them, as I believe was clairvoyant then, and I had checked the spam folder on those days. Now my clairvoyance has dulled and I check my spam folder every other day. What's silly is that other mails from the same source have not been classified as spam, and the content of each of these mails is more or less uniform.
I know you guys believe in the awesomeness of math and all those fancy things, Bayesian filters and all, but surely you should take a lesson from evolution? It has done a real good job no?
I am talking about FALSE POSITIVES, my dear Sirs! It's OK to jump up startled when you see a rope or a vine and think it's a snake. It's deadly to miss a real snake? GEDDIT?
Your spam filters will never be perfect (There's some connection to the halting problem, Godel's theorem, P=NP, and entropy there, I'm just too lazy to explain it), so I will always see some spam in my inbox, that's part of samsaara.
What is stupid is to have something that can classify real mail as spam, especially if it happens to be one from a person who has sent me hundreds of mails, many of which I have starred, re-read, forwarded and so on. This is not an isolated case or issue with gmail in particular, hotmail, yahoo and so on do the same thing - The statement : "Please check your spam folder, I've definitely sent it" is heard quite often.
Big picture folks, big picture - don't get so caught up in your fancy math and cool algorithms when your fundamental assumptions as to what is acceptable behavior is BROKEN!