E-Mail sending to Offcie/Microsoft365 customers not possible - 451 4.7.500 Server busy

Koes 360 Reputation points
2023-10-11T10:38:11.0866667+00:00

Hi,

since this morning 5 am we are not able to send E-mails to office365/Microsoft365 Customers. Our Mails are stuck in our own queue and get the response: host customername.mail.protection.outlook.com 451 4.7.500 Server busy please try again later wit 193.228.149.133 S77719

Can someone check, why we are on an throtteling list with our E-MailServer and remove please?

Exchange Online
Exchange Online

A cloud-based service included in Microsoft 365, delivering scalable messaging and collaboration features with simplified management and automatic updates.


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  1. Alexander Baltazzis 0 Reputation points
    2023-10-11T14:22:06.7733333+00:00

    Same issue from Hetzner 144.76.245.218

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  2. Marcos Vergara 0 Reputation points
    2023-10-11T14:21:49.02+00:00

    In the meantime, we're manually adding reported affected IP addresses to an allowed list to provide immediate relief.

    @outlook.com , please allow this affected IP to your whitelist:

    193.41.7.200

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  3. Marin Heideman | DigiState 0 Reputation points
    2023-10-11T14:21:45.9933333+00:00

    Please also add 185.40.58.180 same problem here

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  4. Iulian Dita 0 Reputation points
    2023-10-11T14:20:55.6866667+00:00

    Please whitelist 80.72.131.26 as well. Thanks!

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