Today on MailOp it was announced that the migration of Microsoft freemail domains to the office 365 backend. Over the next week the mx*.hotmail.com mail servers will stop working. Check your settings, folks, and make sure you’re correctly querying DNS before sending.
At the beginning of the month Microsoft announced that they were deprecating the SmartScreen filters used by the desktop Microsoft mail clients. These are the filters used in Exchange and various version of Outlook mail. This is yet further consolidation of spam filtering between the Microsoft free webmail domains, Office365 hosted domains and self hosted Exchange servers. The online services (hotmail.com, outlook.com, Office365, live.com, etc) have been using these filters for a while. The big change now is that they’re being pushed down to Exchange and Outlook users not hosted on the Microsoft site.
EOP was developed for Outlook.com (and friends) as well as Office365 users. From Microsoft’s description, it sounds like the type of machine learning engine that many providers are moving to.
Microsoft has published quite a bit of information about these filters and how they work on their website. One of the best places to start is the Anti-spam Protection FAQ. Something senders should pay attention to is the final question on that page: “What are a set of best outbound mailing practices that will ensure that my mail is delivered?” Those are all things deliverability folks recommend for good inbox delivery.
Poking around looking at the links and descriptions, there is a host of great information about spam filtering at Microsoft and how it works.
A page of note is their Exchange Online Protection Overview. This describes the EOP process and how the filters work.
Microsoft is still in the process of rolling out new mail servers. One thing that is new about these is some new codes on their error messages. This has led to questions and speculations as to what is going on.
There’s been quite a bit of breakage and delivery failure to various Microsoft domains this month. It started with them changing the MX for hotmail.co.uk, then the MX for hotmail.fr… and both these things seem to have broken mail. I also saw a report this morning that some of the new MXs have TLS certificates that don’t match the hostnames.