Spam?

[chrestomanci]

Hotmail = very little spam any more

That is because they have turned into complete nazis about deleting anything that looks remotely suspicious. People will have sent you non spam email that you have not received because of that.

If you run any sort of email service, and your mail comes from certain domains, from certain countries, or includes even slightly bad words such a 'loan' then any mail you send to hotmail accounts will vanish without a trace. It is imposible to speak to any technical person at hotmail to get your self whitelistied, or even get any explanation as to why a particular bit of mail vansished.

Because of this many online businesses refuse subscriptions from hotmail addresses, because the mail goes missing, and the customers complain when there is nothing the business can do about it.

[Almafi]

That is because they have turned into complete nazis about deleting anything that looks remotely suspicious. People will have sent you non spam email that you have not received because of that.

Spam filtering is a tricky business, like you said, if it is too strict then you get false positives and by not informing the users of what perhaps only just classifies as spam and giving them a chance to say no this is not spam in the future do not treat similar emails as spam is crazy. Perhaps implementing a scalable solution for this is too difficult.