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. Krum Kutsov 0 Reputation points
    2023-10-11T19:34:59.0466667+00:00

    For Bulgaria as well

    Add please these two IPs too:

    195.68.201.23

    195.68.201.24

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  2. Andrea Sirri 0 Reputation points
    2023-10-11T22:25:01.4366667+00:00

    @ microsoft from ITALY

    Please add 77.238.15.41 in whitelist!

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  3. Mareen Eisenmann 25 Reputation points
    2023-10-12T05:00:57.8333333+00:00

    Is this Issue fixed? still have some 452 4.5.3 Too many recipients (AS780090) in the mail queue.

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  4. Lakshmanan Duraisamy 0 Reputation points
    2023-10-12T05:23:24.2166667+00:00

    Hi,

    Still queue is showing the same issue and we try to restarted transport services of ( Mailbox and Edge transport) Please advise!

    Date Received: 10/12/2023 8:10:35 AM

    Expiration Time: 10/14/2023 8:10:35 AM

    Last Error: 451 4.7.500 Server busy. Please try again later from [xxx.xx.xxx.xx]. (S77719) [CB1PEPF00003669.namprd00.prod.outlook.com 2023-10-12T05:15:41.608Z 08DBCA2D71D6CEDD]

    Queue ID: HOSTNAME\89

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  5. Ajay Rooplall 15 Reputation points
    2023-10-12T06:28:10.12+00:00

    Some users may encounter delays receiving external email messages in Exchange Online

    ID: EX680695

    Issue type: Incident

    Status

    Service Restored

    Impacted services

    Exchange Online

    Details

    Title: Some users may encounter delays sending and receiving external email messages in Exchange Online

    User impact: Users may have encountered delays sending and receiving external email messages in Exchange Online.

    More info: Impact was specific to Simple Mail Transfer Protocol (SMTP). Most users would have experienced up to a 1-hour delay; however, in some cases, users may have encountered delays of up to 24 hours. Additionally, the email sender may have received a Non-Delivery Report (NDR) with a "451 4.7.500 Server busy" error message, and their attempt to retry delivery of the email may have been delivered up to 24 hours later.

    Final status: We’ve completed our deployment of the change, which was a targeted reversion of the code issue causing impact. Users should now be experiencing mitigation, though some residual delays may still occur over the next hour as the change completes.

    Scope of impact: Impact was specific to some users who were served through the affected infrastructure. The issue affected users Worldwide and only for a portion of IP addresses, therefore not all users experienced impact.

    Start time: Monday, October 9, 2023, at 9:00 PM UTC

    End time: Wednesday, October 11, 2023, at 5:00 PM UTC

    Preliminary root cause: A recent service update that was applied to a section of infrastructure responsible for enforcing IP address anti-spam rules contained a code issue, which was resulting in the delays with SMTP email delivery.

    Next Steps:

    • We're further reviewing the recent update to understand how the code issue was introduced and to understand what prevented it from being detected in our update testing and validation procedures, which will allow us to prevent similar issues in future updates.

    We’ll publish a Post-Incident Report for this event within five business days.

    Are you experiencing this issue?

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    3 people found this answer helpful.

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