Outlook/Hotmail Email Delivery Requirements Update

We have implemented corrective measures to address the email delivery issues affecting messages sent to Outlook.com and Hotmail recipients.

Our investigation identified DMARC authentication requirements as the primary cause of the delivery failures, with an additional DNS synchronization issue contributing to the impact on some domains.

Our technical team has completed the necessary corrections for the affected domains, and email delivery has been restored for the impacted services.

We are continuing to monitor email delivery to ensure the changes remain effective and that messages are being delivered successfully to Outlook.com and Hotmail recipients.

We appreciate your patience and understanding while we worked to resolve this issue.

We are continuing to work on a fix for this issue.

Microsoft has recently strengthened email authentication requirements for messages sent to Outlook.com, Hotmail.com, Live.com, and other Microsoft-hosted email services.

As a result, domains that do not have properly configured email authentication records may experience email delivery issues, including message rejection, filtering, or delivery delays.

Customers should ensure the following DNS records are configured and valid for all mail-sending domains:

SPF (Sender Policy Framework)
DKIM (DomainKeys Identified Mail)
DMARC (Domain-based Message Authentication, Reporting and Conformance)
A commonly observed rejection error is:

"Message rejected: Message lacks SPF/DKIM/DMARC authentication records."

This particularly affects customers using externally hosted DNS (Remote DNS/External Nameservers), as these records must be added and maintained with their DNS provider.

Customers are encouraged to verify that all required authentication records are present and fully propagated to avoid email delivery issues when sending to Outlook, Hotmail, or Live recipients.

Reference: https://techcommunity.microsoft.com/blog/microsoftdefenderforoffice365blog/strengthening-email-ecosystem-outlook%E2%80%99s-new-requirements-for-high%E2%80%90volume-senders/4399730

Customers who are using our shared NS have been fixed already.