I failed to spot the other thread running ("Microsoft Blocking") before
sending this. I'm giving olcsupport.office.com a shot ... but if there
are any other things I should be doing I'd appreciate the advice.
Thanks!
On Fri, Feb 20, 2026 at 3:34 PM Matthew Pounsett <[email protected]> wrote:
>
> I'm suddenly getting 550 errors for mail addressed to @outlook.com users
> claiming my mail server's IP address is on a block list and referencing
> S3150, which I assume is an error code. The error message also has a link
> to http://mail.live.com/mail/troubleshooting.aspx#errors for more
> information.
>
> S3150 isn't mentioned on that page. Through a bunch of searching I have
> found a thing claiming to be the Office 365 Anti-Spam IP Delist Portal at
> https://sender.office.com/. But, when I go through the steps there I'm
> told my IP is not blocked.
>
> Does anyone know more about this than I do? Anyone from Outlook here that
> could reach out and help me figure out what's going on?
>
>
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