Sorry about the Linkedin one (it was partially mine, and other like me's, fault).
You see, I signed up for many Linkedin groups and then realised that they were sending me too many emails. I removed all of the emails in Linkedin and then found that this would take at least a week before I stopped getting the emails. I waited two weeks, the emails had not stopped and so I classified them as spam.
The issue is that Google is using collaborative filtering, which will tend to weight such emails more highly as spam given that I and others have noted them as spam. Its normally quite effective, but you do need to check your spam box quite often. This isn't because the algorithm doesnt work, its just because of noise created by people using the spam button inappropriately for your use cases.
You see, I signed up for many Linkedin groups and then realised that they were sending me too many emails. I removed all of the emails in Linkedin and then found that this would take at least a week before I stopped getting the emails. I waited two weeks, the emails had not stopped and so I classified them as spam.
The issue is that Google is using collaborative filtering, which will tend to weight such emails more highly as spam given that I and others have noted them as spam. Its normally quite effective, but you do need to check your spam box quite often. This isn't because the algorithm doesnt work, its just because of noise created by people using the spam button inappropriately for your use cases.