Hello everyone, I'm reaching out to ask if anyone on this list may have contacts at Microsoft who could help us escalate a persistent deliverability issue.
Since last Thursday, more than 40 IPs from the same range have been blocked by Microsoft servers. The SMTP response looks like this: 5.7.1 Unfortunately, messages from [143.55.230.150] weren't sent. Please > contact your Internet service provider since part of their network is on > our block list (S3140). You can also refer your provider to > http://mail.live.com/mail/troubleshooting.aspx#errors. [Name=Protocol > Filter Agent][AGT=PFA][MxId=11BBF5965B0435E6] [ > DB1PEPF000509FE.eurprd03.prod.outlook.com 2025-09-24T08:53:32.892Z > 08DDFACB2E2D3F0D] Key details: - The issue has persisted for nearly a week. - Multiple support tickets were opened; each time the response was that the IPs were mitigated, but bounces continued. - Follow-ups on those tickets have not brought progress. - The affected IPs are shared across many clients in different subpools. - Our internal analysis shows no drastic changes in volume or quality of traffic. We've already taken proactive measures, but they have not resolved the problem. At this point, we're hoping someone on this list might have a contact at Microsoft or experience in escalating such cases that could help us get more actionable feedback. Any help or guidance would be greatly appreciated. Thank you in advance, Boris Pavlov
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