Microsoft cracks down on bulk email with strict new Outlook rules

I’ve got some bad news for you, email administrators -- your Monday may be getting a lot worse. You see, starting today, Microsoft has officially begun rejecting high-volume emails that don’t meet its new authentication rules.

Here’s the deal. If you send more than 5,000 messages per day to Outlook.com addresses (including hotmail.com and live.com) and you’re not properly set up with SPF, DKIM, and DMARC, your emails may never arrive. Yikes.

As you can see, Microsoft is strictly enforcing these bulk email rules, with no leeway. Until now, questionable messages might have ended up in junk or spam folders. Now, they’ll instead be bounced entirely with an error message.

This change is clearly aimed at cutting down spam, spoofing, and phishing. While that is appreciated, it will unfortunately also impact marketers, newsletter publishers, and businesses that rely on mass email. Even if your emails are totally legit, failing these checks means you could be silenced.

Thankfully, the rules are pretty straightforward. Your SPF record must clearly identify which IPs can send on your domain’s behalf. DKIM must sign the message with a valid key. And DMARC needs to be published, with alignment to either SPF or DKIM. Preferably both. Without all three in place, Microsoft will silence you.

And don’t assume you’re safe just because you use a third-party service, either. Even if your DNS records aren’t right, you’ll still be on the chopping block. Even things like broken unsubscribe links, outdated mailing lists, or too many DNS lookups in your SPF record could put you at risk. And no, folks, being on a Safe Senders list won’t protect you.