Overview
If Outlook can send but cannot receive, outbound connectivity is working but incoming delivery, filtering, storage, or synchronization still may be failing. Start by checking the mailbox on the web rather than assuming Outlook itself is broken.
Why this happens
This pattern can occur when the mailbox is full, incoming mail is redirected by rules, junk filtering moves messages, Outlook is not synchronizing new mail, or Exchange Online is experiencing a delivery issue.
Before you begin
- Confirm a message can actually leave the mailbox.
- Record a known missing inbound message.
- Keep any sender bounce message.
- Do not reset the Outlook profile before testing the mailbox directly.
Click-by-click troubleshooting
Step 1: Verify the mailbox receives mail on the web
Action: Sign in to Outlook on the web in a private browser window. Send a controlled test message to the affected mailbox from another approved account.
Why this matters: This bypasses desktop Outlook and tests Exchange Online delivery directly.
What to look for: Watch Inbox, Junk Email, and All folders for the test message.
Expected result: If the message arrives on the web, Exchange delivery works and the desktop client becomes the main suspect.
Step 2: Check mailbox quota
Action: In Outlook on the web, open Settings > General > Storage if available and review any quota warning.
Why this matters: A mailbox may still allow some actions while approaching or reaching a receive quota.
What to look for: Look for a full mailbox or warning that storage limits have been reached.
Expected result: The mailbox should have available storage for new inbound messages.
Step 3: Review rules and forwarding
Action: Open Outlook on the web > Settings > Mail > Rules and Settings > Mail > Forwarding.
Why this matters: Rules or forwarding can move, redirect, or delete inbound messages while outbound mail continues normally.
What to look for: Look for unexpected move, delete, redirect, or forwarding actions.
Expected result: No unexpected mailbox rule or forwarding setting should explain the missing mail.
Step 4: Check desktop Outlook status
Action: Open Outlook and verify the bottom status bar. Select Send/Receive > Send/Receive All Folders.
Why this matters: Outlook may be sending queued mail but failing to synchronize new content correctly.
What to look for: Look for Working Offline, Disconnected, Trying to connect, or send/receive errors.
Expected result: Outlook should show Connected and synchronize new mail without errors.
Step 5: Compare Outlook on the web with desktop Outlook
Action: Open the same folder in both clients and compare the newest message timestamps.
Why this matters: This directly identifies whether the desktop cache is behind the server mailbox.
What to look for: Look for recent mail visible on the web but absent from desktop Outlook.
Expected result: The comparison should clearly identify a client synchronization problem if the web mailbox is current.
Step 6: Check Exchange service health if scope is broad
Action: If authorized and multiple users are affected, open Microsoft 365 Admin Center > Health > Service health.
Why this matters: Exchange Online incidents can affect inbound delivery across many mailboxes.
What to look for: Look for mail-flow or Outlook incidents matching the timeframe.
Expected result: You should know whether escalation is local, mailbox-specific, tenant-wide, or provider-side.
What to look for
- Web receives mail but desktop does not: Outlook synchronization issue.
- No web delivery and sender gets bounce: mail-flow issue.
- Mailbox full: capacity issue.
- Unexpected rules or forwarding: configuration or possible security concern.
When to stop
When to contact IT
Contact J3 Systems Group if mail does not arrive on the web, mailbox storage is full, unexpected forwarding is present, Outlook remains out of sync, or multiple users are affected. Include article code KB-05.002 and results from web versus desktop testing.
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Contact J3 Systems GroupAuthoritative references
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