Outage in Cloudflare
Email Security delivery impacted by Spamhaus listing
Resolved MajorIncident Report
Summary AI Generated
Cloudflare's Email Security service (Zero Trust/Area1) experienced a ~2.4-hour delivery disruption after IPs in the 134.195.26.0/23 block were listed by Spamhaus, causing downstream systems that use Spamhaus filtering to reject legitimate emails. Microsoft 365 customers without properly configured connectors were particularly affected. The issue was resolved once Spamhaus removed the listings, with Cloudflare monitoring propagation to downstream systems.
We are currently investigating an issue where customers that use Spamhaus for additional filtering of email downstream from the Cloudflare Email Security service are rejecting emails from IPs in the 134.195.26.0/23 block. This IP block should be allowed for all customer downstream systems to avoid treating the Email Security service as an originator of mail. We recommend all Cloudflare Email Security customers disable Spamhaus filtering in downstream systems.
Components affected
Cloudflare Sites and Services Cloudflare Email Security (Zero Trust) Cloudflare Email Security (Area1)Trusted by 1,000+ teams
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Latest Updates ( sorted recent to last )
MONITORING
about 10 hours ago - at 08/12/2026 04:48PM
All IPs previously listed by Spamhaus are now clean. Monitoring the propagation of that change to downstream systems.
INVESTIGATING
about 10 hours ago - at 08/12/2026 04:30PM
We are continuing to investigate this issue.
Customers using O365 will be impacted only if they have not completed the required setup. Please check your setup and ensure the connector includes all egress IPs:
https://developers.cloudflare.com/cloudflare-one/email-security/setup/pre-delivery-deployment/prerequisites/m365-email-security-mx/#2-configure-enhanced-filtering
INVESTIGATING
about 12 hours ago - at 08/12/2026 03:07PM
We are continuing to investigate this issue.
INVESTIGATING
about 12 hours ago - at 08/12/2026 03:04PM
We are currently investigating an issue where customers that use Spamhaus for additional filtering of email downstream from the Cloudflare Email Security service are rejecting emails from IPs in the 134.195.26.0/23 block. This IP block should be allowed for all customer downstream systems to avoid treating the Email Security service as an originator of mail. We recommend all Cloudflare Email Security customers disable Spamhaus filtering in downstream systems.
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