Outage in SparkPost
Microsoft Mail Delivery Delays and Temporary Rejections
Resolved MinorIncident Report
Summary AI Generated
SparkPost experienced elevated temporary rejection rates for emails delivered to Microsoft-hosted addresses (Outlook.com, Hotmail, etc.) due to an industry-wide issue on Microsoft's side that caused IP rate limiting and delivery delays. The incident lasted 23.8 hours and affected mailbox provider services, with Microsoft acknowledging and actively investigating the problem. Microsoft resolved the issue by making additional changes on February 26th to remediate the IP rate limiting and rejection problems.
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
Components affected
SparkPost Mailbox Provider Service InterruptionNeed to monitor SparkPost outages?
- Monitor all your external dependencies in one place
- Get instant alerts when outages are detected
- Be the first to know if service is down
- Show real-time status on private or public status page
- Keep your team informed
Latest Updates ( sorted recent to last )
RESOLVED
about 8 hours ago - at 02/27/2026 05:38PM
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.
MONITORING
1 day ago - at 02/26/2026 05:55PM
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
Latest SparkPost outages
Elevated 5xx Transmissions API error rates and latency for some SparkPost customers (US hosted only) - 3 days ago
Outbound message delivery is delayed/slow for some SparkPost customers (US hosted only) - 3 days ago
Outbound message delivery is delayed/slow for some SparkPost customers (US hosted only) - 7 days ago
Outbound message delivery is delayed/slow for some SparkPost customers (US hosted only) - 9 days ago
SSO Login Failures Due to reCAPTCHA Configuration Issue - about 1 month ago
The Status Page Aggregator with Early Outage Detection
With IsDown, you can monitor all your critical services' official status pages from one centralized dashboard and receive instant alerts the moment an outage is detected. Say goodbye to constantly checking multiple sites for updates and stay ahead of outages with IsDown.
Start free trialNo credit card required · Cancel anytime · 6020 services available
Integrations with
