Microsoft Deliverability Just Got Tougher… here’s what it means for you.
Hold on to your inboxes, folks... best practices are no longer best — they’re required.
Microsoft just made that (even more) clear by announcing bulk email sender requirements that mirror the ones released by Google and Yahoo last year.
To be clear, this isn't a sudden shift. The writing’s been on the wall for a while now.
And starting May 5th, Microsoft will begin rejecting emails from high-volume senders (above 5,000 emails per day) that don’t comply with their new requirements.
You can check out the full announcement, or just keep reading to catch all the high notes. Here's the scoop.
(More) Email Rejections Are Coming — Here’s Why...
Major mailbox providers are aligning around one thing: protecting their users. And it’s getting a lot harder to do that when senders aren’t playing by the rules.
To be clear, having your emails rejected by Microsoft is not new behavior. In fact, one might say it’s a rite of passage as an email marketer. But this is a notable shift from the “Junk folder” approach we’ve seen from Microsoft in the past when emails were properly authenticated.
So, if you’ve been dragging your feet, now’s the time to get moving or Microsoft won’t even let you in the door.
This Has Been a Long Time Coming
If you’ve already been on top of the Google and Yahoo requirements, this is more of a "yep, we expected that" moment. Both of those giants rolled out similar rules over a year ago.
And while Apple hasn't issued a formal announcement like the others, their filters have consistently prioritized well-authenticated, low-complaint mail. Which is to say, they're already rewarding good behavior (and quietly punishing bad senders).
That said, unlike the others, Microsoft has put unique emphasis on the “Reply-To” address (details below).
So, let’s talk about how you can get all your lil’ email duckies in a row before May 5th.
What Microsoft’s Requiring...
If you send bulk email (more than 5k messages per day) to Microsoft domains, you need to ensure you’re compliant with the following practices… or else.
Here’s a rundown of the most important aspects:
#1 - Authenticate Your Sending Domain with SPF, DKIM, and DMARC
If you're not already set up, what are you waiting for? These three protocols are your basic email protection, verifying that your messages are actually coming from you (and not some shady character in a dark alley).
Microsoft’s requirements are essentially the same as Yahoo and Google’s, so if you’re compliant there, you’re in good shape. But if not, now’s the time to get these records aligned and functioning properly.
💌 SPF and DKIM are the baseline. They let mailbox providers (and your recipients) know that an email coming from you is legit and not some scammer pretending to be you. Need a refresher on email authentication? Go here.
💌 Set your DMARC policy needs to be at least ‘p=none,’ but don’t stop there. That just tells mailbox providers you’re monitoring for failures. To actually protect your brand (and stop spoofers), move to ‘quarantine’ or ‘reject’ when you’re ready. Go here if you aren’t sure what those last couple of sentences mean.
#2 - Use Valid "From" and "Reply-To" Addresses
Here’s where Microsoft introduces something that seems subtle, but actually matters: you’re required to ensure that either the “From” or “Reply-To” address is legitimate, reflects your sending domain, and can accept replies.
Per Microsoft’s own words:
“Ensure the ‘From’ or ‘Reply‐To’ address is valid, reflects the true sending domain, and can receive replies.”
To be clear, that’s either/or, not both. And mailbox providers don't actually care what you call these addresses (e.g. newsletter@ or no-reply@) as long as they’re valid email addresses and at least one of them accepts replies. Also make sure it’s not misleading. Which is to say, don’t use willyoupleasereply@ when you really mean dontyoudarereply@.
Go Beyond This Requirement to Benefit Your Recipients (and Your Business)
That said, while you may technically meet the requirement with just one functional address, there’s a strong case for maintaining both. Mailbox providers (and recipients) pay close attention to how well you manage replies… especially when it comes to building trust and keeping complaint rates low. Even if Microsoft isn’t performing deep technical audits (and let’s be honest, they could if they wanted to), signals like high complaint-to-response ratios or reply bounces can tell them plenty.
If you're using noreply@, sure — technically you're compliant (assuming the “From” or “Reply-To” address works). But you're also slamming the door on a channel that can offer incredible insight into what your customers care about. Not to mention the amount of brands who’ve been able to strengthen their relationship with subscribers simply by accepting and responding to their replies.
I'll give you an example...
A skincare company saw sales drop on a popular product after making subtle changes to its packaging. Nobody was buying it and they didn't know why... until they dug into their email replies and support tickets, where people were complaining about the bottle. They still loved the product itself, but the bottle was dispensing this very costly face cream way too quickly and customers didn't want to "waste their money". They changed the bottle top and BOOM, it was back to a best seller.
So, what did we learn, class? Compliance with mailbox provider requirements and local/global legislation is good. But listening to your subscribers and treating them accordingly is better. If you have a way to get feedback from customers, USE IT!
#3 - Offer a One-Click Unsubscribe
Microsoft is also requiring that emails contain a working one-click unsubscribe link (just like Google and Yahoo). The goal is to help recipients opt out easily and quickly — no hoops to jump through. This is part of a broader push to ensure senders respect recipients’ preferences and keep their lists healthy.
Note: there are a few definitions of one-click unsubscribe floating around, which has been super confusing to a lot of people. The one being referred to as part of everybody’s requirements is RFC 8058. Don’t bother figuring out what an RFC is… just know it’s a nerdy technical standard for making the one-click unsubscribe button work like it should.
Will This Tank My Inbox Placement?
Yes. No. Well, maybe.
It’s hard to say for sure since enforcement doesn’t start with Microsoft for a few more days. But I can tell you how it went down when Yahoo and Google rolled theirs out…
💌 Some senders saw no change. If you were already following the best practices (clean lists, authenticated domains, proper email structures) chances are you saw no difference in deliverability. These changes were essentially a formality for you.
💌 Some saw a lift. Senders who embraced authentication, list hygiene, and better engagement practices reported slight improvements in inbox placement and open rates. This wasn’t a huge jump, but enough to notice that these changes were in the right direction.
💌 Some struggled. The real pain point was for senders who hadn’t kept up with best practices. Non-compliant senders, particularly those using shared IPs with poor reputations, found themselves struggling to hit inboxes. Their emails often landed in spam, and open rates took a hit.
Here’s how I see that playing out for Microsoft’s roll-out…
💌 For senders already following best practices, the impact should be relatively small… non-existent, really.
If you’ve already implemented authentication standards and keep your lists clean, your deliverability will stay strong.
Make sure you have a working "Reply-To" address and then it's back to business as usual.
👏 For senders who’ve been ignoring best practices, it’s time to get with the program!
Compliance isn’t optional anymore. It’s essential to reaching the inbox with major mailbox providers. If you're not compliant by May 5th, your emails will start getting rejected outright by Microsoft.
Based on comments made by other providers speaking at last week’s Deliverability Summit, other major providers will follow suit soon enough.
How to Stay in Recipient Inboxes
In short, don’t wait until you see rejections to act. A few ways to prepare for the big day (and beyond)...
#1 - Audit Your Authentication
Even if you’ve done the work for Google and Yahoo, it’s helpful to double-check your domain’s DNS settings from time to time.
You can use tools like Word to the Wise’s aboutmy.email and Valimail’s domain checker can help confirm that your SPF, DKIM, and DMARC records are in place and compliant.
You can also do this by looking at the email headers of an email sent from your live production environment (where you normally send your mail).
Here’s how to view your email headers. I recognize today's lesson is about Microsoft, but I'm primarily a Gmail user so just deal with it. ¯\_(ツ)_/¯
Step 1: When an email’s open within your Gmail inbox, click the 3 little dots in the upper right corner and select ‘Show original’.
Step 2: Gmail will open a new tab in your browser showing the details below.
If you see a ‘pass’ result for your SPF, DKIM, and DMARC, you’re good!
If you see ‘fail’ anywhere, that’s a problem you’ll need to dig into with your ESP, IT person, or your favorite deliverability consultant (I can introduce you to folks, if needed).
#2 - Check Your Unsubscribe Links
Make sure they’re working properly!
This doesn’t just make you compliant, it helps you avoid deliverability issues stemming from spam complaints.
If you aren’t offering a simple way to unsubscribe (via the RFC 8058 one-click unsubscribe), it’s time to make that a priority.
#3 - Clean Your Lists
Yes, this is another reminder, because a tidy list means fewer complaints and better inbox placement. So, clean your lists… regularly! Remove invalid email addresses, manage your bounces, unsubscribes, and spam complaints.
This is an ongoing effort that should already be in your workflow. If it’s not, make it so!
#4 - Monitor Your Performance Data
Now more than ever, it’s essential to watch your email performance closely. Start with your ESP dashboard, and check it regularly so you know what it looks like when something changes.
You can also use tools like SocketLabs Spotlight to monitor deliverability and catch any issues before they snowball.
The most likely thing you’ll notice if you’re not compliant with Microsoft’s rules is a rejection.
There are a bunch of different terms your ESP might use to describe this: bounced, blocked, rejected, failed, etc, but essentially you’re looking for a case where less messages than usual have been successfully delivered.
Looking Ahead
With so many things changing in the past few years, you might be thinking, “ugh, what next?” And I hear you.
But it’s important to put these stricter requirements into perspective: Microsoft, Yahoo, Apple, and Google aren’t just doing this for fun, promise.
They’re making a concerted effort to protect their users from spam, fraud, and phishing attacks by enforcing authentication and responsible sending because most of the sending world didn’t listen when these tactics were simply recommended as best practices.
I know, I know, email best practices (now requirements)... BORING. The good news?
If you’ve been complying with the guidelines posted by Google and Yahoo, you're in a great position to tackle Microsoft’s new requirements with relative ease.
But keep in mind, just because you're “sending it right" today doesn't mean you should stop checking.
The real challenge isn’t checkin’ boxes and suppressing your eye rolls about best practices — it’s embracing a more holistic approach to email strategy (ahem… respecting your recipients, getting permission, keeping your lists clean, and maintaining a high standard of engagement that aligns with your actual email goals).
As always, if you need help making sure you’re compliant with all of these requirements (or doing anything else email-related), don’t hesitate to reach out. I’m here to help you send it right!
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