sending emails to addresses such as live.com, outlook.com, and hotmail.com

Question

Hello,

Messages we send to live.com addresses are being rejected. We suspect we're being blocked by Microsoft. We don't see any other blocking elsewhere. Here's the error message, DS3PEPF0000C37A.mail.protection.outlook.com a rejeté votre message vers les adresses de courrier suivantes :

[Heurtebis Juliette (******@libourne.fr)] Votre message n'a pas été remis en raison d'un problème d'autorisation ou de sécurité. Il a pu être rejeté par un modérateur, l'adresse n'accepte peut-être de courrier que provenant de certains expéditeurs, ou une autre restriction peut empêcher sa remise.

DS3PEPF0000C37A.mail.protection.outlook.com a généré cette erreur : Unfortunately, messages from [89.90.126.210] 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][MxId=11BAA0397D94CADA] [DS3PEPF0000C37A.namprd04.prod.outlook.com 2025-02-22T10:44:50.422Z 08DD501CC324AE32]

Thank you.

Answer 1

Hello Pascal BLANCHARD,

the error message shows that your IP address 89.90.126.210 is on a Microsoft blacklist (error code S3150). This means that Microsoft has classified the mail server or part of the network as potentially problematic.

Possible solutions:

1. Check the IP address for blacklists:

Check whether your IP is on general blacklists, e.g. via:

https://mxtoolbox.com/blacklists.aspx

2. Microsoft delisting request:

• Request removal from the blacklist:

https://sender.office.com/

• There you can request a review and unblocking of your IP address.

3. Check SPF, DKIM & DMARC:

• Microsoft could block your emails if the authentication mechanisms are not configured correctly.
• Check your SPF, DKIM and DMARC entries with:

https://mxtoolbox.com → “SPF Record Lookup”, “DKIM Lookup”, “DMARC Lookup”

4. Contact your internet provider:

• If you have no control over your outgoing IP address (e.g. with shared hosting or a dynamic IP), your ISP may need to help.
• If the mail server is managed by an external provider, you should contact their support.

5. Contact Microsoft support:

• If nothing helps, you can contact Microsoft support:

https://support.microsoft.com

If you send emails for business purposes, another option would be to use Microsoft 365 or another professional mail server to avoid blacklisting problems.

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