SparkPost incident
Microsoft Mail Delivery Delays and Temporary Rejections
SparkPost experienced a minor incident on February 26, 2026 affecting Mailbox Provider Service Interruption, lasting 23h 42m. The incident has been resolved; the full update timeline is below.
Affected components
Update timeline
- monitoring Feb 26, 2026, 05:55 PM UTC
We are currently seeing elevated temporary rejection rates for email delivered to Outlook.com, Hotmail, and other Microsoft-hosted addresses. Microsoft has acknowledged the issue and is actively investigating. This is a industry-wide issue and not isolated to any specific account. We will continue to monitor and update this page as we receive more information. Next update: When Microsoft posts a resolution or Bird observes delivery rates normalizing
- resolved Feb 27, 2026, 05:38 PM UTC
Microsoft has confirmed that they made additional changes the night of Thursday, Feb 26th that should have remediated most IP rate limiting and rejection issues. If you are still seeing impacts, please reach out via your normal support channels and our team can investigate and escalate with Microsoft.