[zAy0LfpBZLC8mAC]

> How would you implement a spam filter?

What do you mean "implement"? You are aware that there exists free spam filtering software that you can install, like, say, spamassassin (which has been around longer than gmail)?

> Maybe but being slightly over aggressive means a world in terms of user happiness.

Dropping legitimate emails is good for user happiness? You have strange users. I imagine if the post office decided to throw away some letters "slighty over aggressive[ly]" ... there are people who would be happy if that happened?

> Think about email before Gmail. How much junk did you see in your inbox? There is a lot LESS today.

I see maybe one to three spam mails per day, with nearly zero false positives (maybe one per year). And that's without gmail. Obviously, I could reduce that to zero spam, at the cost of increased false positives, which is not a sensible option as far as I am concerned, deleting three mails per day isn't really all that much work.