Some Outlook.com and Hotmail users aren’t receiving emails because messages sent to them are bouncing, with senders being told their emails failed an authentication check. I’ve personally observed this behavior when a business struggled to reach me because its emails bounced. I’m told that senders get an error saying their email failed an SPF check.
I thought it was just me, but when I glanced over Microsoft’s forums and Reddit, I noticed that other people were also having issues receiving emails on Outlook.com and Hotmail.
Windows Latest understands that emails have been rejected since at least November 5, and I’ve been able to reproduce the issue on November 8.
If you’re affected, you may have trouble sending emails to valid contacts or receiving emails from them. In most cases, it’s unclear what actually happened, but when you dig deeper and check the logs, you’ll realize that emails were not sent or received due to an authentication error.
It is worth noting that some senders say they get the error even when their email domains already have valid authentication records. So even if everything looks good on paper, you may not be getting all your emails. In some cases, messages go through when the sender tries again.
“Domains with valid SPF, DMARC and DKIM are being rejected. It only happens for a small percentage of the emails (probably depends on which Microsoft server your message gets routed to),” one user wrote in Microsoft’s forum.
“I strongly suspect this is a Microsoft issue. We have only come across this when sending to Hotmail accounts. We first had rejections yesterday; resending the email was sometimes successful. Today I have had an email which was sent to 2 recipients; no issue with the Gmail recipient, but the Hotmail recipient was bounced,” another user noted.
One Microsoft 365 customer explained that they had been emailing their client for three weeks, but Outlook suddenly rejected a reply. When the same user tried to email their own Hotmail address, they ran into the same error. However, both Gmail and a separate Exchange mailbox accepted their test messages, according to their report on Microsoft Q&A.
There are hundreds of similar complaints, and most align with what I have personally been observing as well. It also looks like some emails are delivered later, but only when the sender tries again.
The catch with unreliable emails is that you don’t realize there’s a problem unless you’re told about it. If you’re on the receiving end, you might only find out when someone contacts you another way. One Outlook.com user said about half the clients who had emailed them since November 5 had received a rejection.
Why are Outlook and Hotmail suddenly flagging SPF and blocking emails?
For those unaware, SPF checks whether a server is allowed to send emails on behalf of a domain. For example, if someone tries to send an email using a domain they don’t own, SPF can help flag that the sending server isn’t authorized. Without checks like this, you’d be staring at hundreds of emails looking legitimate from people who don’t even own the domain.
But the Outlook errors point to an SPF failure even when some senders say their records are correct. For example, some bounce notices show 550 5.7.23 and tell you to ask your IT admin to check SPF. Here’s one of the alerts appearing in the reports:
550 5.7.1 Message rejected: Message lacks SPF/DKIM/DMARC Auth Records (AS9031519)
Also, if you’re wondering if only Microsoft 365, Outlook, or Hotmail senders are affected, you’re wrong. If someone uses another provider, such as Zoho, to email an Outlook.com address, they might still run into these problems.
One Outlook.com user said a message from a Zoho sender was rejected at 3:50 p.m. The sender tried again at 4:09 p.m., and this time it arrived. The successful message showed that SPF and DKIM passed.
You can’t patch a clock that isn’t even broken, and this is a good example of the problem people are seeing. But the successful message’s results don’t tell us exactly what happened to the earlier attempt.
Users wonder if Microsoft changed Outlook or its email settings
There are no statements pointing to an intentional change, and I don’t think Microsoft would make Outlook emails unreliable at a time when it’s already facing scrutiny over Windows. It’s possible that a temporary issue is affecting some users, but Microsoft hasn’t publicly confirmed the cause.
There are certain rules that could prevent emails from getting delivered. For example, if you send more than 5,000 emails a day to Microsoft’s consumer email services using a particular domain, your messages can be blocked if they don’t comply with SPF, DKIM, and DMARC requirements.
However, some affected senders say they’re far below that threshold, but reconfiguring or verifying their authentication records appears to work.
“Same issue, started 4 AM PST yesterday. I checked SPF, DKIM, and DMARC – seemed like everything was okay. I checked them again, and it looks like my org’s domain was missing a DMARC DNS entry. I set it to p=none for now. And that seems to have fixed it, no failures with lots of tests an hour in so far,” a Reddit user wrote.
If you’ve run into the error, you may want to ask the sender to check their authentication records and share the full bounce message with their email provider or Microsoft support. In any case, I’d recommend retrying after a few minutes, as this trick has actually worked for some people, but there’s no confirmed fix for all the reports right now.
