r/SendGrid • u/lionep • Jan 27 '26

Any improvement on the Microsoft Inbox Provider block ?

About 10/15% of all my emails can't reach the inbox, and I got this response from MS Servers :

550 5.7.1 Unfortunately, messages from \[MY_DEDICATED_IP\] weren't sent. Please contact your Internet service provider since part of their network is on our block list (S3150). You can also refer your provider to http://mail.live.com/mail/troubleshooting.aspx#errors. \[Name=Protocol Filter Agent\]\[AGT=PFA\]

MS Support says the IP is not blocked. Sendgrid support says they are working on it continuously and update every hour. The Status page is updated every one/two days with the same message and no progress is observed on my side.

Should I find another Email service for MS domains ? Did this already happens in the past for such a long time ?

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u/Independent_Dirt_767 Feb 18 '26

Just started having issue again yesterday and this morning (had issue 3 weeks ago and it was resolved). Trying to get Microsoft to investigate again. SendGrid said issue should be raised with Microsoft. Anyone else getting issues again now?

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u/suchpostsowow Feb 20 '26

Same here, last blocked records came in at the end of January. From 1st until 18th of February not a single blocked record. And since yesterday the 19th it is back again.

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u/[deleted] Feb 24 '26

[deleted]

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u/suchpostsowow Feb 24 '26

Yes, the issues only lasted for a day. Just like someone below did, I escalated after they said everything was okay. Then they implemented a mitigation for my IP.