NDUS Office 365 - Message not being delivered to some domain

We have resolved the incident. Thank you for your patience.

You will need to resend any messages that were not delivered earlier today.

Current status: Microsoft has disabled an anti-spam rule that they suspect may be blocking some users from sending outbound email messages, and confirming with some users who initially reported the issue to confirm if disabling this rule remediated impact.

Scope of impact: Some users attempting to send email messages to users outside of their organization may be impacted.

Next update by: Monday, April 10, 2023, 4:00 PM (#20747780)

User impact: Users are unable to send outbound email messages in Exchange Online.

More info: Impact is specific to sending email messages to addresses outside of your organization. Email messages sent from users within your organization to other users within your organization aren’t impacted.

Current status: Our review of NDRs provided by affected users is leading us to suspect that an anti-spam rule isn't behaving as expected and contributing to impact. We're investigating further to confirm this and to identify resolution options.

Scope of impact: Your organization is affected by this event, and any user attempting to send email messages to users outside of your organization is impacted.

Next update by: Monday, April 10, 2023, 2:00 PM CDT (#20747780)

Microsoft is still working on the issue.

The next update will be 2:00 p.m. CDT

(#20747780)

This issue started at about 10:30 a.m. CDT.

Microsoft is aware of and working on this issue, as it is affecting many Office 365 tenants.

The next update will be 1:00 p.m. CDT

(#20747780)

We are receiving reports of some email messages not being delivered to some domains.

We are looking into this.