This back from tech support at my hosting lot - it looks as if Hotmail really should get the boot!
"Like most of the large free email providers, hotmail will often block legitimate emails as part of their "anti-spam". If the recipient uses email for anything important, a reliable email provider should be used who will not block emails without the users permission. Attempting to get any information from hotmail about why it was blocked will prove futile, the same as with most of the other big free providers."
I guess they get what they (don't) pay for
