Outlook.com Is Silently Bouncing Email From Domains Without DMARC
Outlook.com Is Quietly Rejecting Email from Domains Without DMARC
Since November 5, 2026, Microsoft's consumer mail services — Outlook.com, Hotmail, Live and MSN — have been rejecting some messages from domains that lack a DMARC record, with no announcement and no clear error. The 550 5.7.1 bounce hits ordinary small senders, not just bulk mailers, and only intermittently, so mail can vanish without anyone noticing. The fix is a single TXT record: v=DMARC1; p=none.
Microsoft refuses only part of the mail from an affected domain. One message to a Hotmail address goes through, the next one bounces, and a resend may succeed.
- Neikius
Outlook.com is also rejecting mail based on blocklists that are not public and you essentialy cannot get yourself out. My VPS provider is pretty much entirely blocked and their regular blocklist process says we are golden so nothing to unblock.
Outlook.com and similar are an anathema to email. This is why they tell you not to run a mail server .
On the other hand rejecting domains without dmarc is fine. Just not happy it is silent.
- codethief
Outlook.com has quietly dropped[0] emails from certain domains/IPs for years, even with SPF/DKIM/DMARC all properly set up and no history of spam. As someone who's administering their own mail server, Outlook has been the bane of my existence.
[0]: As in: They accepted the email just fine (according to the logs) but it still didn't end up in the recipient's mailbox.
- stephbook
Sounds like something every mail sender should have done already.
Good for Microsoft customers and I don't care one bit for the lazy people who have to late-patch now.
- klodolph
I set up DMARC on my personal domain so long ago I can't even remember when I did it. 10 years+?
I had kinda assumed that a lot of providers would start rejecting domains without DMARC support. I'm surprised it's happening this late.
- dwm
They're not rejecting them quietly. They're sending 5xx permanent delivery failures.
- stevefan1999
Well, if we can get a more relaxed email self hosting experience with the DMARC enforcement, I'd say it is a good trade-off in exchange with freedom of speech, rather than accepting the risk of spamming.
These days, hosting a proper mail server isn't really that hard, thanks to Stalwart https://stalw.art/. I did it to my Talos Linux cluster located on LA and utilizing idle resources. It is pretty great
- verandaguy
This is interesting. At some point, I think it'll be desirable to give increasing positive weight to emails with the DPF/DKIM/DMARC trifecta configured, since those are least likely to be problem emails (spam or phishing), but I wonder what the best avenue is to actually make that the default. It's almost certainly not this kind of unannounced cutoff.
Email is, I think, among the most distributed popular online services, and there's a ton of stuff that's legacy, self-managed, or otherwise janky. Supporting SPF, DKIM, and DMARC does put a burden on independent operators, but is it an undue or unreasonable one in the current landscape? Or is it just the new cost of doing business?
- green-salt
I thought they've been doing this for years, along with gmail/etc. I basically just added setting up the correct DNS records as part of business when sending emails externally.
- himata4113
I actually totally agree with this. There's too much risk involved with scams disguised as legitimate services because the developers of said service couldn't be bothered to add 1 or 2 dns records.
Although there seems that there hasn't been any communication which is the bad thing here. However, nobody looks at those and sending detailed emails back seems like a good enough solution.
- Grimeton
The only mistake people make here is to accept that the problem is on their end even after Microsoft has accepted the e-mail but silently discarded it. This leads to the customer impression that the mistake happens on their end and not on Microsoft's.
When I see in my logs that the e-mail has been successfully delivered to their MTA then I don't have a problem.