Service desk · Incident · Email/M365
Cannot Send / Receive Email
User is completely cut off from email — every minute of silence costs the business.
- Priority
- Critical
- Handled by
- Help Desk Technician (L2)
- SLA, hours
- 0.5 respond · 1 plan · 4 resolve
- Hands-on effort
- 45 min
- Reach
- 2 of 2 tool classes through a connector · remote
- Self-service
- Guided: the user can fix it with Claudia walking them through it.
What it looks like
- User reports they cannot send messages — mail sits in Outbox or bounces with an NDR.
- Incoming mail stopped arriving; colleagues say their messages went through but the user sees nothing.
- Outlook shows 'Disconnected' or 'Trying to connect…' persistently after restarting the client.
- User receives a delivery failure notification referencing their own address or domain.
- Mobile mail app stopped syncing while the browser and desktop client also fail — ruling out a single-client issue.
What causes it
- Mailbox disabled, license removed, or account blocked in Microsoft 365 admin center or Entra — frequently triggered by a licensing audit or offboarding error.
- MFA or Conditional Access policy change that broke legacy auth or a specific client profile.
- Outbound spam hold placed by Microsoft's service on the mailbox or tenant connector after a compromised-account sending burst.
- DNS or MX record misconfiguration — especially after a domain renewal, registrar migration, or SPF/DKIM update.
- On-premises or third-party mail gateway (Mimecast, Proofpoint, etc.) misconfiguration or expired certificate blocking relay.
Resolution plan · 7 steps, each with its check
- 01
Check M365 Service Health Dashboard (admin.microsoft.com → Health → Service health). Confirm whether Exchange Online shows an active incident or advisory.
CheckNo active Exchange Online degradation shown — or, if one exists, record the incident ID and set user expectation. Do not proceed to tenant-level changes while a platform incident is open.
- 02
Scope the blast radius: test send/receive for 2–3 neighboring users in the same department via OWA (outlook.office.com). Do NOT touch Outlook desktop yet.
CheckOWA confirms whether the failure is isolated to one mailbox or affects a group. This gates the next step — single-user vs. multi-user paths diverge here.
- 03
In M365 admin center, verify the affected user(s) have a valid Exchange-capable license assigned and the Exchange mailbox status is Active. In Entra admin center, review Conditional Access policies recently modified that target Exchange or the affected user's group.
CheckLicense shows assigned with no error state. No CA policy change in the last 24–48 hrs that would block Exchange auth — or, if one exists, it is identified as the root cause and its scope confirmed.
- 04
In Exchange admin center, inspect the mailbox: quota status, litigation hold configuration, and any transport rules or connectors modified recently. Flag any rule targeting the affected sender/recipient domain.
CheckQuota is not at limit. No transport rule or connector misconfiguration explains the block. If a rule/connector is the cause, revert or correct it and confirm the change takes effect (EAC shows updated config; allow 2–5 min propagation).
- 05
In the email security gateway admin (Defender for Office 365, Mimecast, Proofpoint, or equivalent), pull delivery logs for the affected mailbox and domain. Look for policy blocks, connector rejections, or quarantine hits in the delivery window.
CheckDelivery logs show successful inbound/outbound events after remediation — or the blocking policy is identified, corrected, and a test message passes clean through the gateway log.
- 06
If OWA now works but Outlook desktop still fails, run Microsoft Support and Recovery Assistant (SaRA) against the affected Outlook profile to identify auth corruption, profile errors, or cached credential conflicts.
CheckSaRA scan completes without blocking findings — or identifies and remediates a specific profile/auth issue. Outlook desktop sends and receives a test message successfully.
- 07
Document root cause, affected window (start → resolution time), and remediation action in the ticket. Note any CA policy, transport rule, connector, or gateway policy change made, including who/when the change originated.
CheckTicket notes contain: root cause category, scope (user count), timeline, and the specific config change made. No related users remain impacted per step-2 scope check.
Closed when
- Affected mailbox sends and receives a live test message via both OWA and Outlook desktop — not just one client.
- At least 2 neighboring users in the same department confirmed unaffected (or, if they were affected, confirmed restored).
- M365 Service Health shows no active Exchange Online incident, or any platform incident is fully resolved and the advisory is closed.
- Root cause is documented in the ticket with the specific change (CA policy, transport rule, connector, gateway policy, license) and the originating event — sufficient for a post-incident review without re-investigation.
Skills it needs
- Exchange Online Administration · Intermediate
- Incident Management · Intermediate
- M365 Tenant Administration · Intermediate
- DNS Troubleshooting · Junior
- Email Security (DMARC/DKIM/SPF + Gateway) · Junior
- Service Level Management · Junior
Consoles and access
- Identity verification / caller authorizationConfirm affected user identity and authorization to act on mailbox
- Microsoft 365 admin centerUser Admin role (view/manage users, licenses, service health)
- Exchange admin center (EAC)Exchange Administrator role (mailbox status, mail flow, message trace)
- Microsoft Entra admin centerSecurity Reader or Global Reader (sign-in logs, Conditional Access review)
Where the human checkpoint sits
Claudia starts supervised on every MSP, and your team raises the level on evidence. For service desk work the model permits up to L2 Supervised.
- L0 Advisory
- L1 Copilot
- L2 Supervised
- L3 Guardrailed
- L4 Autonomous
The model's reasoning for that ceiling, verbatim: “Per-ticket scope on high-volume, mostly reversible work. L1 required a human to approve every single ticket classification, which is not defensible for triage. L3 only for read-only deflection.”
