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 InterruptionTrusted by 1000+ teams
Need to monitor SparkPost outages?
Stop finding out about outages from your users. Monitor 6,320+ cloud services and get alerted the moment something breaks.
Ready to take control?
Start Free Trial
No credit card required
Set up in 2 minutes
14-day free trial
Latest Updates ( sorted recent to last )
RESOLVED
about 2 months 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
about 2 months 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
Increased bounce or delay rate for Apple domains - 9 days ago
Email delivery in US region affected - about 1 month ago
Outbound message delivery is delayed/slow for some SparkPost customers (US and EU regions) - 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 · 6320 services available
Integrations with
