Some Emails to Outlook or Hotmail Suddenly Bouncing? Here's What You Need to Know

If your business has suddenly started having trouble sending emails to Hotmail, Outlook.com or Live.com addresses, you're not alone.

Since 5 November 2026, businesses and email providers around the world have reported that Microsoft is rejecting some incoming emails due to missing email authentication records, particularly DMARC.

The concerning part? This is affecting ordinary businesses sending everyday emails, not just companies sending thousands of marketing messages.

That means an invoice, quotation, appointment confirmation or even a simple reply to a customer could fail to arrive.

Fortunately, there's an easy way to check whether your business domain might be affected.

Check your business email domain for free with Mint's Email Health Checker

What's Changed with Microsoft Email?

Microsoft has been tightening its email security requirements for some time.

In May 2025, Microsoft began enforcing stricter authentication requirements for domains sending 5,000 or more emails per day to its consumer email services.

These requirements included three important email security technologies: SPF, DKIM and DMARC.

However, since 5 November 2026, email administrators have reported that Microsoft's consumer email services are also rejecting some messages from much smaller senders whose domains don't have DMARC configured.

This affects email addresses such as:

• @outlook.com
• @hotmail.com
• @live.com
• @msn.com

Some senders are receiving an error similar to:

550 5.7.1 Message rejected: Message lacks SPF/DKIM/DMARC Auth Records (AS9031519)

Unlike an email going into someone's junk folder, these messages are rejected outright. The intended recipient never receives them.

Microsoft hasn't officially confirmed whether this represents a permanent change to its requirements or an issue with its email filtering systems. There have also been reports of intermittent failures involving domains that already have valid authentication records.

Nevertheless, the reports highlight why businesses should ensure their email security settings are properly configured.

What Is DMARC, and Why Does It Matter?

DMARC stands for Domain-based Message Authentication, Reporting and Conformance.

It sounds complicated, but the purpose is relatively simple: help email providers verify that messages claiming to come from your business are legitimate.

There are three important components to modern email authentication.

• SPF (Sender Policy Framework) identifies which email servers are authorised to send messages on behalf of your domain.
• DKIM (DomainKeys Identified Mail) adds a digital signature to outgoing messages, allowing receiving servers to verify that the message was signed by an authorised domain and hasn't been modified in transit.
• DMARC builds on SPF and DKIM, checking whether authentication aligns with the domain shown in the sender's email address. It also allows domain owners to tell receiving providers how to handle messages that fail authentication.

These technologies help protect businesses against email spoofing, phishing and impersonation.

For example, without appropriate protections, criminals may find it easier to send messages pretending to come from your business, potentially tricking customers into paying fraudulent invoices or sharing confidential information.

DMARC has been recommended for years, but the recent Microsoft delivery problems are a reminder that email authentication can affect your ability to communicate with customers, not just your security.

Could Your Business Be Affected?

Potentially, yes.

Even if your business uses Microsoft 365 for email, it doesn't automatically mean every authentication requirement is properly configured.

It's possible to have Microsoft 365 working perfectly for everyday email while your domain is missing a DMARC record.

And Microsoft 365 isn't the only service to consider.

Your business might also send emails through accounting software, website contact forms, CRM platforms, booking systems or marketing services.

Each of these services needs to be considered when configuring email authentication.

If your domain doesn't have DMARC configured, you may be more exposed to the delivery problems currently being reported.

Check Your Domain in Seconds

We've made it easy to check your domain's email health.

Simply visit our free checker: emailhealth.mint.net.nz

Enter your business domain name, such as yourcompany.net.nz, and review the results, paying particular attention to DMARC.

If your domain is missing a DMARC record, it's worth getting this resolved promptly.

Even if you're not currently experiencing email delivery failures, taking action now can help prevent problems and improve your overall email security.

What Should You Do If DMARC Is Missing?

DMARC is configured through your domain's DNS records.

For a domain without DMARC, the initial configuration can be relatively straightforward. A basic monitoring policy such as v=DMARC1; p=none is often a suitable starting point. Adding a reporting address, for example rua=mailto:dmarc@yourcompany.net.nz, means you'll receive reports showing who is sending email as your domain, including any services you'd forgotten about.

However, simply adding a record isn't the complete solution.

Your SPF and DKIM settings also need to be checked to ensure your legitimate email systems authenticate correctly.

This is especially important if your business sends emails from several different services.

A monitoring-only DMARC policy doesn't instruct recipients to block fraudulent messages. Stronger policies can offer better protection, but should only be introduced after your legitimate sending systems have been verified.

Before you change anything that could affect email delivery, let us check the complete configuration. We'll make sure every system that sends email for your business is covered first.

And if messages have already bounced, they'll generally need to be resent once the underlying problem is resolved.

Need Help? Chat to Us

If your Email Health Checker results show missing records, or your emails are suddenly bouncing back from Outlook or Hotmail addresses, we're here to help.

At Mint, we help New Zealand businesses manage Microsoft 365, Google Workspace, email security and the technology they rely on every day.

We can review your domain's email authentication settings, identify configuration problems and help ensure your legitimate emails are being delivered correctly.

Start with our free Email Health Checker.

If something doesn't look right, give us a call or send us an email.

• Phone: 09 222 0220
• Email: Contact Mint Technology

Existing Mint customers can also contact our helpdesk at support@mint.net.nz.