Mail Flow Failures
Inbound/outbound blocking, delays, and routing failures. Includes NDRs, throttling, and connector checks.
Exchange Online: Prevent $50K–$500K+ mail flow incidents
Rapid diagnosis and safe remediation for mail flow failures, NDRs, throttling, and delivery issues. Average MTTR: 15–30 minutes, preventing extended downtime and compliance exposure.
View Diagnostic Guides
DLP & Journaling
Data loss prevention, message journaling, and compliance hold issues. Diagnostic decision trees for silent drops and journal failures.
- Coming soon
Distribution Lists & Groups
Group expansion failures, dynamic distribution list issues, and member delivery problems.
- Coming soon
When to Use This Section
Use these guides when experiencing mail flow disruptions, delivery delays, or non-delivery reports (NDRs) in Exchange Online. Common scenarios include messages stuck in transport queues, 550 5.1.1 recipient rejections, throttling errors during bulk sends, NDR 554 policy blocks, or delayed delivery affecting time-sensitive workflows. These diagnostics cover both inbound and outbound mail flow, connector misconfigurations, transport rule conflicts, and tenant-level throttling policies. Start here for any P1 incident involving undelivered or delayed email.
Guides
Decision trees, error codes, and root cause patterns.
Response SLAs
Incidents routed to principal engineers; diagnostic-first approach.
P1: Critical Mail Block
Target: 10m acknowledgment, 30m diagnostic plan
No inbound/outbound mail, zero delivery, connector failure.
P2: Partial Delivery
Target: 30m acknowledgment, 90m diagnostic plan
Delays, routing failures, NDRs for some recipients, throttling.
P3: Advisory
Target: 2h acknowledgment, runbook provided
Preventive diagnostics, config review, optimization tips.