E-Mail sending to Outlook.com customers not possible - 451 4.7.500 Server busy

Question

Dear Sir/Madam,

since this morning 9 am in Hong Kong we are not able to send E-mails to outlook.com 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 xxxxxxxx

Pls assist to fix the problem asap because this fully affect our business operation.

Can you advise any mail address to me for send our ip and domain to you and add your white list ?

Best Regards

Billy Lee

Answer 1

Known Issue:

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

EX680695, Last updated: October 11, 2023 at 10:22 AM EDT

Estimated start time: October 9, 2023 at 5:00 PM EDT

Affected services

Exchange Online

Issue type

Incident

Issue origin

Microsoft

Status

Service degradation

Manage notifications for this issue

User impact

Users may encounter delays receiving external email messages in Exchange Online.

October 11, 2023 at 8:22 AM EDT

Title: Some users may encounter delays receiving external email messages in Exchange Online User impact: Users may encounter delays receiving external email messages in Exchange Online. More info: Affected users may see a "451 4.7.500 Server busy" error message. Current status: We’ve identified that a recent service update, applied to a section of infrastructure responsible for enforcing IP address anti-spam rules, contains a change which is inadvertently causing impact. We’re developing and validating a fix to revert to the most recent stable service version to remediate impact. In parallel, we’re continuing to manually add reported affected IP addresses to an allowed list to alleviate impact in the short term. Scope of impact: Impact is specific to some users who are served through the affected infrastructure. Start time: Monday, October 9, 2023 at 5:00 PM EDT Root cause: A recent service update, applied to a section of infrastructure responsible for enforcing IP address anti-spam rules, contains a change which is inadvertently causing impact.