Tessian incident
Delays Processing Some Inbound and Outbound Emails
Tessian is currently experiencing a major incident affecting M365 Add-in and Core Email Protection API and 1 more component, which began 2h ago. The vendor's full update timeline is below.
Affected components
Update timeline
- monitoring Jun 12, 2026, 06:01 PM UTC
Status: Monitoring Proofpoint investigated elevated error rates processing inbound and outbound emails on our US Server. On June 12 2026 from 14:30 UTC to 16:19 UTC, ~2% of emails sent or received failed to process. Proofpoint Engineering have remediated the issue, and is currently monitoring. For Core Email Protection API - this mean impacted inbound emails were not initially submitted for scoring, did not create a security event, and could not be found in Investigation & Respond. Missed emails are currently being re-submitted, effectively translating to a delay in processing and remediation where applicable. For Adaptive Email DLP - this means reporting for M365 add-in user responses may be temporarily inaccurate on the timeline of a security event. A small percentage of checks done by the M365 Add-in quickly timed out and failed open during the impact window. For customers using the Gateway, these check would have been routed to and completed by the Gateway. Affected components Core Email Protection API (Degraded performance) M365 Add-in (Degraded performance) Reported Emails (Degraded performance) Investigate and Respond - Email Search (Degraded performance)