For the sake of the argument: if you get 3000 messages of spam per day it means that it takes a lot of effort to check them all.
Also, as you receive a lot of spam, the distribution is highly skewed towards spam, so it is unlikely you find a false positive because there are a lot more true positive, not because the false positives are absent.
So there is a chance you are getting false positives, but have failed to spot them (I know it happens to me).
I get noticed by other means, e.g.
- I sent you the link on gmail
- no you didn't
- check your spam folder
- I just did!
- check again!
- alright.. ah err, yes you did
Also, as you receive a lot of spam, the distribution is highly skewed towards spam, so it is unlikely you find a false positive because there are a lot more true positive, not because the false positives are absent.
So there is a chance you are getting false positives, but have failed to spot them (I know it happens to me).