More details on blocked emails
When emails are preblocked or spam preblocked, we don't know why, so it's not easy to improve or make changes.
David Keegan commented
I agree, it seems this information is available if you got to All Contacts, then search for the contact who had the blocked email, then click on that contact, then click on the blocked email. But this is a long trip to take, would be nice if this was easily accessible from the main view.