Microsoft spent much of the past week rejecting legitimate emails sent to Outlook.com, Live, and Hotmail accounts due to what appears to be overly aggressive IP reputation filtering or faulty blocklist rules. According to The Register, many senders received 550 errors claiming their networks were blocked, preventing delivery of invoices, notifications, and authentication emails. From the report: A block list is a good thing. It helps stem the flow of spam from networks or addresses associated with junk email. However, the confusing thing for our reader is that his company was not on Microsoft's naughty step for email. A look at Microsoft's Smart Network Data Service (SNDS) showed no issues w...