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.


175 answers

Sort by: Oldest
  1. Alain D 21 Reputation points
    2023-10-11T14:51:36.8966667+00:00

    @outlook.com Please allow the following IP addresses :

    193.....

    145.....

    Thanks.

    Oct 11, 11pm : Mails are gone from Queue. Don't know if the antispam rule or ip whitelist that did the trick.

    Was this answer helpful?

    0 comments No comments

  2. Seidel, Johannes 0 Reputation points
    2023-10-11T14:52:24.1133333+00:00

    Hi,

    same issu here.

    Please whitelist the following ip´s:
    213.61.227.182
    213.61.227.189
    213.61.227.190

    Was this answer helpful?

    0 comments No comments

  3. Johnny Authement 0 Reputation points
    2023-10-11T14:54:26.7133333+00:00

    @outlook.com Please whitelist 69.2.42.130

    Was this answer helpful?


  4. Dillor Zaarour - Global IT 0 Reputation points
    2023-10-11T14:57:30.6833333+00:00

    @Microsoft support @Outlook please whitelist 199.66.225.65, 199.66.225.5, 199.66.225.4,199.66.225.50, 199.66.225.18, 199.66.225.8, 199.66.225.2, 199.66.225.3, 199.66.225.25, 199.66.225.23, 199.66.225.17.

    Thank you -

    Was this answer helpful?

    0 comments No comments

  5. Sergey Severinchik 0 Reputation points
    2023-10-11T14:58:21.18+00:00

    Pls, add to whitelist 195.209.37.228

    Was this answer helpful?

    0 comments No comments

Your answer

Answers can be marked as 'Accepted' by the question author and 'Recommended' by moderators, which helps users know the answer solved the author's problem.