Microsoft Office 365 Affecting Mail Flow

Microsoft appears to have changed the Exchange Online perimeter, which may have introduced graylisting behavior. Microsoft's Exchange Online Advisory EX444758 is believed to be the reason for the changes. The start time of the advisory is 9:40 AM which coincides with email delivery delays appearing in Mailprotector's logs.

Mailprotector has not changed or altered any email delivery operations. The email delays are the result of Microsoft changing the behavior of the Exchange Online perimeter.

Any domain still impacted by Microsoft's changes today should implement the Inbound Connector for Mailprotector. The KB article that provides the information to implement the connector is found at https://support.mailprotector.com/hc/en-us/articles/115005484203-Office-365-Inbound-Connector.

Please configure the Inbound Connector and ensure it is enabled. Mailprotector will update recommendations and documentation to emphasize the importance of using the Inbound Connector. The connector will provide additional trust information to Microsoft and reduce the chances of delaying email.

Microsoft has "grey listed" some of Mailprotector's inbound transport IP addresses, causing mail delivery delays. The team is working diligently with Microsoft to understand why the addresses have been grey-listed and request status removal.

Partners trying to improve mail flow can implement the inbound connector to the tenant. The inbound connector is not a resolution but can enhance the trust between Mailprotector and Microsoft's Exchange perimeter. Please use the following link for the connector KB article.

https://support.mailprotector.com/hc/en-us/articles/115005484203-Office-365-Inbound-Connector

We are receiving reports that a Microsoft Office 365 issue is delaying email delivery. Emails are being queued at Mailprotector.

Emails are automatically retried using an exponential backoff method. Once Microsoft's service issue has been resolved, emails will automatically be delivered.

Mailprotector is continuing to monitor updates from Microsoft for more information.