[German]A quick note to readers who use Microsoft email accounts. A reader informed me this morning that there are massive delivery problems to Hotmail addresses. There is also a second reader report in the discussion area asking about email problems at Microsoft. Microsoft is receiving an increasing number of reports of problems from administrators. Anyone affected?
A first hint from a blog reader
Blog reader Manfred R. contacted me late this morning and asked if I had heard anything about Hotmail problems. The reader wrote: "Perhaps other email administrators have had the same experience as I just did. It seems that Microsoft is currently experiencing various problems with email delivery, especially to @hotmail.com recipients." The reader states that he received the following status message from Hornet Security regarding email delivery to hotmail.com
451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation
The reader comments: "It looks to me as if Microsoft is currently experiencing a 'glitch' on its Hotmail.com servers. The MX Toolbox did not show me any blacklist entries or bad IP reputations for the relevant sending IPs from the Hornet Security range." He then sent me the following excerpt from the messages.
2026-02-25T08:16:41Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.73.17];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD8ED89C25A13] [AMS0EPF0000019D.eurprd05.prod.outlook.com 2026-02-25T08:16:42.739Z 08DE6C76D27C4E74] 2026-02-25T08:17:01Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.41.27];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD7FC1AA31CA3] [SJ1PEPF00002316.namprd03.prod.outlook.com 2026-02-25T08:17:04.409Z 08DE6BFE17249F93] 2026-02-25T08:18:02Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.41.1];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD87E7566EDDD] [SJ1PEPF00001CDC.namprd05.prod.outlook.com 2026-02-25T08:18:06.234Z 08DE6C3F44579568] 2026-02-25T08:19:02Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.9.22];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD9952DB5AAAE] [BL6PEPF00020E62.namprd04.prod.outlook.com 2026-02-25T08:19:03.890Z 08DE6CCAA01C6393] 2026-02-25T08:20:02Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.9.22];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCDA2E1DC6D88F] [BL6PEPF00020E61.namprd04.prod.outlook.com 2026-02-25T08:20:05.076Z 08DE6D1717E2B42F] 2026-02-25T08:21:01Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.68.11];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD7BEFBEF23D3] [DB1PEPF000509E6.eurprd03.prod.outlook.com 2026-02-25T08:21:03.856Z 08DE6BDF8C82EEC5] 2026-02-25T08:22:02Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.68.38];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD80C4A1C51C8] [DU2PEPF00028D02.eurprd03.prod.outlook.com 2026-02-25T08:22:03.713Z 08DE6C06331F67BF] 2026-02-25T08:24:01Z;TLS;hotmail-com.olc.protection.outlook.com[52.101.73.152];451 4.7.650 The mail server [94.100.133.56] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD7F1DFA2646F] [AMS1EPF0000008F.eurprd05.prod.outlook.com 2026-02-25T08:24:02.946Z 08DE6BF8FDEF1A66] For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD8ED89C25A13] [AMS0EPF0000019D.eurprd05.prod.outlook.com 2026-02-25T08:16:42.739Z 08DE6C76D27C4E74] https://aka.ms/postmaster -> substrate.office.com
Another reader comment in my German blog
A reader who wished to remain anonymous asked in the discussion forum whether anyone else was currently experiencing problems with email delivery to MS domains. He wrote that he was receiving the following messages from the mail server about a temporary rate limit due to IP reputation.
4.7.650 The mail Server [xxx.xxx.xxx.xxx] has been temporarily rate limited due to IP reputation. For e-mail delivery information, see https://aka.ms/postmaster (S775) [Name=Protocol Filter Agent][AGT=PFA][MxId=11BCD7CB2BCF7832]
He states that he is affected in a corporate environment. Checking his own servers for sending using MX Toolbox reports that everything is fine.
The reader notes that the reports seem to be increasing and has linked to this forum thread. Someone else posted a similar entry there on February 25, 2026, and others affected confirm the problem.
