S3150 is what you get when you don't slow down after seeing 4xx. 😊
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> ? -----Original Message----- From: mailop <[email protected]> On Behalf Of Michael Brown via mailop Sent: Friday, February 20, 2026 2:15 PM To: [email protected] Subject: Re: [mailop] [EXTERNAL] Anyone from Outlook? S3150 block list mirage On 2026-02-20 17:01, Michael Wise via mailop wrote: > It’s throttling. Any evidence of that? I note Microsoft's own documentation (https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fsubstrate.office.com%2Fip-domain-management-snds%2Fpostmaster%2Ftroubleshooting%23errors&data=05%7C02%7Cmichael.wise%40microsoft.com%7C31539444dc03468ced8208de70ce0d31%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C639072227479757896%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=Ej280VM5BR7FLfBpaixOwxgSQ7cyvGbeHAIVPlBMUKI%3D&reserved=0<https://substrate.office.com/ip-domain-management-snds/postmaster/troubleshooting#errors>) indicates this kind of situation would receive a different message, e.g.: 421 RP-001 The mail server IP connecting to Outlook.com server has exceeded the rate limit allowed. Reason for rate limitation is related to IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help. 421 RP-002 The mail server IP connecting to Outlook.com server has exceeded the rate limit allowed on this connection. Reason for rate limitation is related to IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help. 421 RP-003 The mail server IP connecting to Outlook.com server has exceeded the connection limit allowed. Reason for limitation is related to IP/domain reputation. If you are not an email/network admin please contact your Email/Internet Service Provider for help. (not that I expect Microsoft to follow their documentation, but :shrug:) M. -- Michael Brown Civilized Discourse Construction Kit, Inc. https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.discourse.org%2F&data=05%7C02%7Cmichael.wise%40microsoft.com%7C31539444dc03468ced8208de70ce0d31%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C639072227479774629%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=W%2BpKQmaBuJeeiutd7%2B8NJPJK7gQED8lwK9reXy3xogc%3D&reserved=0<https://www.discourse.org/> _______________________________________________ mailop mailing list [email protected]<mailto:[email protected]> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Flist.mailop.org%2Flistinfo%2Fmailop&data=05%7C02%7Cmichael.wise%40microsoft.com%7C31539444dc03468ced8208de70ce0d31%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C639072227479785878%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=c4uo7wnfLq15%2BDqQmtjfM%2FGEpAxjMJOm52D9sDh4Phw%3D&reserved=0<https://list.mailop.org/listinfo/mailop>
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