As I hinted previously, no. I no longer can comment on the Consumer side of the house.
Aloha, Michael. -- Michael J Wise Microsoft Corporation| Spam Analysis "Your Spam Specimen Has Been Processed." Open a ticket for Hotmail<http://go.microsoft.com/fwlink/?LinkID=614866> ? From: Michael Denney <[email protected]> Sent: Friday, February 20, 2026 3:49 PM To: Michael Wise <[email protected]> Cc: Matthew Pounsett <[email protected]>; [email protected] Subject: Re: [mailop] [EXTERNAL] Anyone from Outlook? S3150 block list mirage You don't often get email from [email protected]<mailto:[email protected]>. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> I checked mail logs going back to December 2025 - and I see exactly zero 421 errors. As a matter of fact we have exactly zero 4XX responses from Outlook - network wide, but I do see 550's with the error 3150. Are you sure this is properly implemented? Feels half-baked as though it was AI vibe coded. Thank you, Michael Denney MDDHosting LLC http://www.mddhosting.com/ On Feb 20, 2026, at 6:29 PM, Michael Wise <[email protected]<mailto:[email protected]>> wrote: … slower. Aloha, Michael. -- Michael J Wise Microsoft Corporation| Spam Analysis "Your Spam Specimen Has Been Processed." Open a ticket for Hotmail<http://go.microsoft.com/fwlink/?LinkID=614866> ? From: Michael Denney <[email protected]<mailto:[email protected]>> Sent: Friday, February 20, 2026 3:27 PM To: Michael Wise <[email protected]<mailto:[email protected]>> Cc: Matthew Pounsett <[email protected]<mailto:[email protected]>>; [email protected]<mailto:[email protected]> Subject: Re: [mailop] [EXTERNAL] Anyone from Outlook? S3150 block list mirage You don't often get email from [email protected]<mailto:[email protected]>. Learn why this is important<https://aka.ms/LearnAboutSenderIdentification> We’ve also been seeing this. Clients that have dedicated mailing IPs that haven’t had issues and have been established for a long time. No new increased flows - normal transactional emails. Even opened a ticket and got told everything was fine. If it’s throttling - why not just say that? So what do we tell customers? “Microsoft things you’re sending too much mail and there’s nothing you can do but send less mail.”? Thank you, Michael Denney MDDHosting LLC https://www.mddhosting.com/ On Feb 20, 2026, at 6:11 PM, Michael Wise via mailop <[email protected]<mailto:[email protected]>> wrote: It’s IP specific, and is dynamically assigned. Aloha, Michael. -- Michael J Wise Microsoft Corporation| Spam Analysis "Your Spam Specimen Has Been Processed." Open a ticket for Hotmail<http://go.microsoft.com/fwlink/?LinkID=614866> ? From: Matthew Pounsett <[email protected]<mailto:[email protected]>> Sent: Friday, February 20, 2026 2:50 PM To: Michael Wise <[email protected]<mailto:[email protected]>> Cc: [email protected]<mailto:[email protected]> Subject: Re: [EXTERNAL] [mailop] Anyone from Outlook? S3150 block list mirage On Fri, Feb 20, 2026 at 5:01 PM Michael Wise <[email protected]<mailto:[email protected]>> wrote: It’s throttling. Slow down your deliveries. The rate limit must be incredibly low, if that's the case. We sent less than 1500 messages to outlook.com<http://outlook.com/> mail servers all day on February 20th. If it is a rate limit, then please share where the rate limit is documented, so that I can set the throttle appropriately. I can't keep under a rate limit if I don't know what it is. And if it's a rate limit, why are we getting 500 errors instead of 400? That should be a temporary error. _______________________________________________ mailop mailing list [email protected]<mailto:[email protected]> https://list.mailop.org/listinfo/mailop
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