Is Outlook Down? Complete Status Check Guide + Quick Fixes

Outlook emails not syncing?
Can't send or receive messages?
"Disconnected" or "Working Offline" stuck on screen?

Before panicking, verify if Outlook is actually down—or if it's a problem on your end. Here's your complete guide to checking Outlook status and fixing common issues fast.

Quick Check: Is Outlook Actually Down?

Don't assume it's Outlook. 70% of "Outlook down" reports are actually local account issues, outdated app versions, or network connectivity problems.

1. Check Official Sources

Microsoft 365 Service Status:
🔗 status.office.com

What to look for:

  • ✅ "Service is healthy" = Outlook is fine
  • ⚠️ "Service degradation" = Some services affected
  • 🔴 "Service interruption" = Outlook is down

Real-time updates:

  • Exchange Online issues
  • Outlook.com problems
  • Outlook mobile app status
  • Microsoft 365 admin center alerts
  • Regional outages

Twitter/X Search:
🔗 Search "Outlook down" on Twitter

Why it works:

  • Users report outages instantly
  • See if others in your region affected
  • Microsoft 365 Status account responds here

Pro tip: If 1000+ tweets in the last hour mention "Outlook down," it's probably actually down.

2. Check Service-Specific Status

Outlook has multiple services that can fail independently:

Service What It Does Status Check
Outlook.com Free web email status.office.com
Outlook Desktop Windows/Mac desktop app Check Exchange Online status
Exchange Online Business email backend admin.microsoft.com/servicehealth
Outlook Mobile iOS/Android apps Check mobile sync status
Outlook on the web Web client (OWA) outlook.office.com
Microsoft Graph API Email API for developers status.graph.microsoft.com

Your service might be down while Outlook globally is up.

How to check which service is affected:

  1. Visit status.office.com
  2. Look for specific service status (Exchange Online, Outlook, etc.)
  3. Check "Incident History" for recent issues
  4. Subscribe to status updates (admin center)

3. Test Different Connection Types

If Outlook web works but desktop app doesn't, it's likely your app/network.

Platform Test Method
Web (OWA) outlook.office.com or outlook.com
Desktop Launch Outlook app, check connection status
Mobile Try Outlook on 4G/5G (bypass WiFi)

Decision tree:

Web works + Desktop fails → App/profile issue
Web fails + Desktop fails → Account/server issue
Mobile works + Desktop/Web fail → Local network problem
Nothing works → Outlook/Exchange is down

Common Outlook Error Messages (And What They Mean)

"Trying to connect..." / "Disconnected"

What it means: Outlook can't reach Microsoft's email servers.

Causes:

  • Network connectivity issues
  • Firewall blocking Outlook
  • VPN interference
  • Exchange Online service disruption
  • Expired credentials

Quick fixes:

  1. Check if outlook.office.com loads in browser
  2. Click "Send/Receive All Folders" (Ctrl+M)
  3. Restart Outlook
  4. Check network connection
  5. Disable VPN temporarily
  6. Check Microsoft 365 status page

Error 0x800CCC0E: "Cannot connect to server"

What it means: Outlook can't connect to incoming/outgoing mail server.

Causes:

  • Incorrect server settings (IMAP/SMTP)
  • Firewall blocking ports
  • ISP blocking email ports
  • Server temporarily down

Quick fixes:

  1. Verify server settings:
    • Incoming (IMAP): outlook.office365.com, port 993 (SSL)
    • Outgoing (SMTP): smtp.office365.com, port 587 (TLS)
  2. Check firewall allows ports 993, 587, 443
  3. Test connection in browser: outlook.office.com
  4. Recreate Outlook profile (see Fix #7)

Error 0x8004010F: "Cannot access Outlook data file"

What it means: Outlook can't open or access .pst/.ost file.

Causes:

  • Corrupted data file
  • File in use by another process
  • File permissions issue
  • Antivirus scanning Outlook files

Quick fixes:

  1. Close Outlook completely
  2. Run Inbox Repair Tool (scanpst.exe):
    • Windows: C:\Program Files\Microsoft Office\root\Office16\scanpst.exe
    • Select your .pst file, run scan
  3. Disable antivirus real-time scanning temporarily
  4. Create new Outlook profile (see Fix #7)
  5. Check file permissions on .ost/.pst file

Error 0x80040600: "Unknown error"

What it means: Generic error, usually corrupted Outlook data file.

Causes:

  • Corrupted .pst/.ost file
  • Add-in conflicts
  • Profile corruption

Quick fixes:

  1. Run scanpst.exe (Inbox Repair Tool)
  2. Start Outlook in Safe Mode:
    • Windows: outlook.exe /safe
    • Mac: Hold Option while launching
  3. Disable all add-ins (File → Options → Add-ins)
  4. Create new Outlook profile

"The operation failed. An object cannot be found."

What it means: Outlook can't find folder, email, or attachment.

Causes:

  • Corrupted search index
  • Deleted item still showing in view
  • Sync issue with Exchange
  • Corrupted folder

Quick fixes:

  1. Rebuild search index:
    • File → Options → Search → Indexing Options → Rebuild
  2. Empty Deleted Items folder
  3. Repair folder:
    • Right-click folder → Properties → Clear Offline Items → OK
  4. Force mailbox sync:
    • Send/Receive → Update Folder (F9)

"Your mailbox is full"

What it means: Mailbox has reached storage limit.

Causes:

  • Exceeded mailbox quota (50GB for most Microsoft 365 plans)
  • Large attachments
  • Archive not enabled

Quick fixes:

  1. Check mailbox size:
    • File → Info → Mailbox Settings → Cleanup Tools
  2. Empty Deleted Items permanently
  3. Archive old emails:
    • File → Options → Advanced → AutoArchive Settings
  4. Delete large attachments:
    • Search: hasattachments:yes size:>10mb
  5. Move emails to Archive mailbox (if available)
  6. Contact admin to increase quota

"Cannot start Microsoft Outlook. Cannot open the Outlook window."

What it means: Outlook profile is corrupted.

Causes:

  • Corrupted Outlook profile
  • Navigation pane corruption
  • Outlook crashed during startup

Quick fixes:

  1. Start in Safe Mode: outlook.exe /safe
  2. Reset navigation pane:
    • outlook.exe /resetnavpane
  3. Reset folders:
    • outlook.exe /resetfolders
  4. Create new Outlook profile (see Fix #7)
  5. Reinstall Office (nuclear option)

Authentication Errors: "Enter password" repeatedly

What it means: Outlook can't authenticate with Microsoft servers.

Causes:

  • Expired credentials
  • Multi-factor authentication required
  • Cached credential issue
  • Azure AD authentication failure

Quick fixes:

  1. Sign out and sign in again:
    • File → Account Settings → Remove account → Re-add
  2. Clear credential cache:
    • Windows: Control Panel → Credential Manager → Remove Office credentials
    • Mac: Keychain Access → Delete Microsoft credentials
  3. Check if MFA prompt appeared (check notifications)
  4. Update Office to latest version
  5. Reset password at account.microsoft.com

Quick Fixes: Outlook Not Working?

Fix #1: Restart Outlook (The Classic)

Why it works: Clears connection cache, resets server connections, fixes temporary glitches.

How to do it right:

Windows:

  1. Close Outlook (X button)
  2. Open Task Manager (Ctrl+Shift+Esc)
  3. Find "Outlook" or "OUTLOOK.EXE" → End Task
  4. Also end "Microsoft Exchange" processes if present
  5. Relaunch Outlook

Mac:

  1. Quit Outlook (Cmd+Q)
  2. Force quit if needed: Cmd+Option+Esc → Outlook → Force Quit
  3. Wait 30 seconds
  4. Relaunch

Pro tip: End all Outlook background processes—just closing the window isn't enough.

Fix #2: Check Internet Connection

Outlook needs:

  • Minimum: Stable internet connection (1+ Mbps)
  • Recommended: 5+ Mbps for large attachments
  • Latency: <200ms ping to Microsoft servers

Test your connection:

# Ping Microsoft's email servers (Windows/Mac/Linux)
ping outlook.office365.com

Good response:

Reply from 52.96.4.2: bytes=32 time=35ms TTL=113

Bad response:

Request timed out.

Speed test:
Visit fast.com or speedtest.net

If connection is slow:

  1. Restart router (unplug 30 seconds)
  2. Move closer to WiFi router
  3. Switch to Ethernet cable
  4. Disconnect other devices from network
  5. Contact ISP if consistently slow

Fix #3: Force Send/Receive

Sometimes Outlook just needs a nudge.

Manual sync:

  1. Click Send/Receive tab
  2. Click Send/Receive All Folders (or Ctrl+M)
  3. Watch status bar for errors

Update specific folder:

  1. Click on folder (Inbox, Sent Items, etc.)
  2. Press F9 to update that folder

Check Send/Receive settings:

  1. File → Options → Advanced → Send/Receive
  2. Ensure "Send immediately when connected" is checked
  3. Set automatic send/receive interval (5 minutes recommended)

Fix #4: Check Firewall/Proxy Settings

Outlook needs these ports open:

Port Protocol Purpose
443 TCP HTTPS (Outlook on the web, Modern Auth)
993 TCP IMAP (if using IMAP)
587 TCP SMTP (outgoing mail)
995 TCP POP3 (if using POP3)
80 TCP HTTP redirect

Windows Firewall:

  1. Windows Security → Firewall & Network Protection
  2. Allow an app through firewall
  3. Find "Microsoft Outlook" → Check Private + Public
  4. If not listed: "Allow another app" → Browse to OUTLOOK.EXE
  5. Click OK

Mac Firewall:

  1. System Preferences → Security & Privacy → Firewall
  2. Firewall Options
  3. Find Outlook → "Allow incoming connections"
  4. If not listed: "+" → Add Outlook

Corporate/School Networks:

  • Contact IT department
  • Outlook might be blocked by network policy
  • May need to use VPN or configure proxy settings

Proxy settings:

  1. File → Options → Advanced
  2. Under "Other," uncheck "Allow web services to use proxy"
  3. Or configure corporate proxy if required by IT

Fix #5: Update Office/Outlook

Outdated app = sync issues and security risks.

Check for updates:

Windows:

  1. Open any Office app
  2. File → Account → Update Options → Update Now
  3. Wait for updates to install
  4. Restart Outlook

Mac:

  1. Open Microsoft AutoUpdate
  2. Check for Updates
  3. Install available updates
  4. Restart Outlook

Current version (as of Feb 2026):

  • Microsoft 365: Version 2402 or later
  • Office 2021: Version 16.0.14332 or later

Enable auto-updates:

  • File → Account → Update Options → Enable Updates

Pro tip: Office updates automatically by default, but corporate installations sometimes disable this.

Fix #6: Disable Add-ins

Why it helps: Buggy add-ins cause crashes, slow performance, and sync issues.

Disable all add-ins:

Windows:

  1. File → Options → Add-ins
  2. At bottom, select "COM Add-ins" → Go
  3. Uncheck all add-ins → OK
  4. Restart Outlook
  5. Re-enable one at a time to find culprit

Mac:

  1. Tools → Add-ins
  2. Uncheck all add-ins
  3. Restart Outlook

Start in Safe Mode (faster):

  • Windows: Win+R → outlook.exe /safe
  • Mac: Hold Option while launching Outlook

Common problematic add-ins:

  • Old antivirus plugins
  • Third-party CRM integrations
  • Outdated cloud storage add-ins

Fix #7: Create New Outlook Profile

Why it helps: Corrupted profiles cause 40% of persistent Outlook issues.

Windows:

1. Create new profile:

  1. Close Outlook
  2. Control Panel → Mail (Microsoft Outlook)
  3. Show Profiles → Add
  4. Name: "New Profile"
  5. Enter email address, let Outlook configure automatically
  6. Click Finish

2. Set as default:

  1. "Always use this profile" → Select "New Profile"
  2. OK
  3. Launch Outlook

3. If it works:

  • Old profile was corrupted
  • Import .pst file from old profile if needed:
    • File → Open & Export → Import/Export → Import from another program or file → Outlook Data File (.pst)

Mac:

1. Delete old profile:

  1. Quit Outlook
  2. ~/Library/Group Containers/ → Delete "UBF8T346G9.Office"
  3. ~/Library/Containers/ → Delete "com.microsoft.Outlook"

2. Launch Outlook:

  • Will create new profile automatically
  • Sign in with email/password

Pro tip: This fixes 80% of persistent Outlook issues.

Fix #8: Repair Office Installation

When Outlook keeps crashing or won't start.

Windows:

Quick Repair (faster):

  1. Close all Office apps
  2. Settings → Apps → Microsoft 365 → Modify
  3. Select "Quick Repair" → Repair
  4. Wait 5-10 minutes
  5. Restart computer

Online Repair (thorough):

  1. Settings → Apps → Microsoft 365 → Modify
  2. Select "Online Repair" → Repair
  3. Wait 20-30 minutes (re-downloads Office)
  4. Restart computer

Mac:

  1. Uninstall Office completely
  2. Download fresh installer from office.com
  3. Install
  4. Sign in

Fix #9: Clear Outlook Cache

Why it helps: Corrupted cache causes sync errors, slow performance, search issues.

Windows:

Clear autocomplete cache:

  1. File → Options → Mail
  2. Under "Send messages," click "Empty Auto-Complete List"
  3. OK

Clear OST file (offline cache):

  1. Close Outlook
  2. Navigate to: %localappdata%\Microsoft\Outlook
  3. Delete all .ost files (NOT .pst files—those contain your emails!)
  4. Restart Outlook (will re-sync from server)

Mac:

Clear cache:

  1. Quit Outlook
  2. Finder → Go → Go to Folder
  3. Type: ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile
  4. Delete "Data" folder contents
  5. Restart Outlook

Warning: Deleting .ost files forces full re-sync. May take time for large mailboxes.

Fix #10: Check Account Settings

Verify your email account is configured correctly.

Check account status:

  1. File → Account Settings → Account Settings
  2. Double-click your email account
  3. Click "Test Account Settings"
  4. Watch for errors

Common issues:

  • ❌ "Cannot connect to outgoing mail server" → Check SMTP settings
  • ❌ "Authentication failed" → Re-enter password
  • ❌ "Certificate error" → Accept certificate or update Outlook

Recommended settings for Microsoft 365 / Exchange Online:

Incoming server (IMAP):

  • Server: outlook.office365.com
  • Port: 993
  • Encryption: SSL/TLS
  • Authentication: OAuth2 (Modern Authentication)

Outgoing server (SMTP):

  • Server: smtp.office365.com
  • Port: 587
  • Encryption: STARTTLS
  • Authentication: Same as incoming

For Outlook.com (free accounts):

  • Use same settings as above
  • Modern Authentication should auto-configure

Outlook Email Sync Issues

Issue: Emails Not Sending (Stuck in Outbox)

Troubleshoot:

1. Check for large attachments:

  • Default limit: 20MB for Outlook.com, 25MB for Microsoft 365
  • If too large, use OneDrive link instead
  • Right-click attachment → Send as OneDrive link

2. Check for corrupted message:

  • Open message in Outbox
  • Delete and recreate (copy text first)
  • Try sending to yourself as test

3. Force send:

  • Click Send/Receive → Send All
  • Or Ctrl+M

4. Check offline mode:

  • Look for "Working Offline" in status bar
  • Click "Send/Receive" → Work Offline to toggle

5. Check SMTP server:

  • File → Account Settings → Account Settings
  • Double-click account → More Settings → Outgoing Server
  • ✅ "My outgoing server (SMTP) requires authentication"
  • ✅ "Use same settings as my incoming mail server"

Issue: Emails Not Receiving (No New Mail)

Troubleshoot:

1. Force manual check:

  • Send/Receive → Send/Receive All Folders
  • Or press F9 in Inbox

2. Check send/receive groups:

  • File → Options → Advanced → Send/Receive
  • Send/Receive Groups
  • Ensure your account is in "All Accounts" group
  • Set to check every 5-10 minutes

3. Check rules/filters:

  • Emails might be filtered to other folders
  • File → Manage Rules & Alerts
  • Disable all rules temporarily
  • Check Junk Email, Deleted Items folders

4. Check mailbox full:

  • File → Info → Mailbox Cleanup
  • Empty Deleted Items
  • Archive old emails

5. Check server-side rules:

  • Log in to outlook.office.com
  • Settings → Mail → Rules
  • Check for forwarding or deletion rules

Issue: Calendar/Contacts Not Syncing

Troubleshoot:

1. Check sync settings:

  • File → Account Settings → Account Settings
  • Select account → Change → More Settings
  • Advanced tab
  • ✅ "Download shared folders"
  • ✅ "Use Cached Exchange Mode"

2. Force calendar sync:

  • Right-click Calendar folder → Properties
  • Clear Offline Items → OK
  • Wait for re-sync

3. Check permissions:

  • Calendar might not be shared with you
  • Ask calendar owner to verify permissions

4. Rebuild calendar:

  • Create new Calendar folder
  • Move appointments to new folder
  • Delete old calendar folder

Issue: Search Not Working

Troubleshoot:

1. Rebuild search index:

Windows:

  1. File → Options → Search
  2. Indexing Options → Advanced
  3. Rebuild
  4. Wait 30-60 minutes for completion

2. Check indexing status:

  • Look for "Search results may be incomplete" message
  • If indexing, wait for it to finish

3. Add Outlook to indexed locations:

  1. Control Panel → Indexing Options
  2. Modify
  3. ✅ Microsoft Outlook
  4. OK

4. Restart Windows Search service:

Windows:

  1. Win+R → services.msc
  2. Find "Windows Search"
  3. Right-click → Restart

Mac:

  • Spotlight indexing handles Outlook search
  • System Preferences → Spotlight → Rebuild index

Outlook Mobile App Issues

Issue: Mobile App Not Syncing

Troubleshoot:

1. Force refresh:

  • Pull down on inbox to refresh
  • Check "Last updated" timestamp

2. Check account connection:

  • Settings → Tap account name
  • "Delete Account" → Re-add account
  • Sign in again

3. Check background app refresh:

iOS:

  • Settings → Outlook → Background App Refresh → On

Android:

  • Settings → Apps → Outlook → Battery → Allow background activity

4. Check push notifications:

  • Settings → Notifications → Push notifications → On
  • Check notification settings for Focused Inbox

5. Clear app cache:

iOS:

  • Delete and reinstall app (data syncs from server)

Android:

  • Settings → Apps → Outlook → Storage → Clear Cache

Issue: Mobile App Crashing

Troubleshoot:

1. Update app:

  • App Store / Play Store → Check for updates
  • Update Outlook to latest version

2. Restart device:

  • Power off completely
  • Wait 30 seconds
  • Power on

3. Reinstall app:

  • Delete Outlook app
  • Restart device
  • Reinstall from App Store / Play Store
  • Sign in (emails sync from server)

4. Check device storage:

  • Low storage causes crashes
  • Delete unused apps/photos
  • Need at least 1GB free

Outlook on the Web (OWA) Issues

Issue: OWA Slow or Not Loading

Troubleshoot:

1. Clear browser cache:

Chrome/Edge:

  1. Ctrl+Shift+Delete
  2. Select "Cached images and files"
  3. Clear data
  4. Reload outlook.office.com

2. Disable browser extensions:

  • Try Incognito/Private mode
  • If works, extension is interfering
  • Disable extensions one by one

3. Try different browser:

  • Test in Chrome, Edge, Firefox, Safari
  • Recommended: Edge or Chrome (best compatibility)

4. Check Light version:

  • Settings → View all Outlook settings
  • General → Accessibility
  • ✅ "Use the light version of Outlook"
  • Faster but fewer features

Issue: Can't Open Attachments in OWA

Troubleshoot:

1. Check file type:

  • Some file types blocked for security
  • .exe, .bat, .vbs blocked by default

2. Download instead of preview:

  • Click dropdown next to attachment
  • Select "Download"

3. Check browser popup blocker:

  • Allow popups for outlook.office.com
  • Attachment preview needs popups

4. Try different browser:

  • Edge and Chrome have best compatibility
  • Safari sometimes has attachment issues

Developer Issues: Microsoft Graph API

Issue: API Authentication Failures

Troubleshoot:

1. Check app registration:

  • Azure Portal → App registrations
  • Verify Client ID and Tenant ID correct
  • Check redirect URIs match

2. Verify permissions:

  • API permissions → Microsoft Graph
  • Required: Mail.Read, Mail.Send, etc.
  • Grant admin consent if required

3. Check token expiration:

  • Access tokens expire after 1 hour
  • Refresh token to get new access token
  • Implement token refresh logic

4. Test with Graph Explorer:

Issue: API Throttling / 429 Errors

What it means: Too many API requests.

Limits:

  • 10,000 requests per 10 minutes per app per mailbox
  • Concurrent request limits vary by endpoint

Solutions:

1. Implement exponential backoff:

async function retryWithBackoff(fn, retries = 3) {
  try {
    return await fn();
  } catch (error) {
    if (error.status === 429 && retries > 0) {
      const delay = error.headers['Retry-After'] * 1000 || 2000;
      await sleep(delay);
      return retryWithBackoff(fn, retries - 1);
    }
    throw error;
  }
}

2. Batch requests:

  • Use $batch endpoint
  • Combine multiple requests
  • Reduces total API calls

3. Use webhooks:

  • Subscribe to change notifications
  • Avoid constant polling
  • More efficient than repeated API calls

4. Optimize queries:

  • Use $select to request only needed fields
  • Use $filter to reduce results
  • Implement pagination properly

Issue: Webhook Notifications Not Received

Troubleshoot:

1. Check subscription status:

GET https://graph.microsoft.com/v1.0/subscriptions/{subscription-id}

2. Verify notification URL:

  • Must be HTTPS
  • Must respond to validation within 10 seconds
  • Return 200 OK with validation token

3. Renew subscriptions:

  • Max lifetime: 4230 minutes (3 days) for mailbox resources
  • Implement auto-renewal before expiration

4. Check certificate validity:

  • Notification endpoint needs valid SSL certificate
  • Self-signed certificates not accepted

Issue: SMTP/IMAP Connection Failures

Troubleshoot:

1. Enable SMTP AUTH:

  • Admin center → Users → Active users
  • Select user → Mail → Manage email apps
  • ✅ Authenticated SMTP
  • Save

2. Check server settings:

IMAP:

  • Server: outlook.office365.com
  • Port: 993
  • Encryption: SSL/TLS

SMTP:

  • Server: smtp.office365.com
  • Port: 587
  • Encryption: STARTTLS
  • Auth: Required

3. Use app password for legacy apps:

4. Check tenant settings:

  • Exchange admin center → Mail flow → Connectors
  • Verify SMTP relay configured if needed

Regional Outages: Is It Just Me?

Microsoft has data centers worldwide:

Region Data Centers
North America Multiple (Azure regions)
Europe Amsterdam, Dublin, Frankfurt, Paris
Asia Pacific Singapore, Hong Kong, Tokyo, Sydney
South America São Paulo
Middle East UAE, Qatar

How to check for regional issues:

1. Check DownDetector:
🔗 downdetector.com/status/office-365

Shows:

  • Real-time outage reports
  • Heatmap of affected regions
  • Spike in reports = likely real outage

2. Check Twitter by region:
Search "Outlook down [region]"
Example: "Outlook down New York" or "Outlook down UK"

3. Test from different location:

  • Try mobile hotspot (different network/provider)
  • Ask colleague in different region to test
  • Try OWA from different browser/device

4. Check tenant-specific status:

  • Microsoft 365 admin center → Service health
  • Shows issues affecting your specific tenant
  • More accurate than general status page

When Outlook Actually Goes Down

What Happens

Recent major outages:

  • January 2024: 6-hour Exchange Online outage (authentication issues)
  • September 2023: 4-hour Outlook.com disruption (database failure)
  • March 2023: 8-hour outage (Azure AD authentication failure)

Typical causes:

  1. Azure infrastructure issues
  2. Authentication service failures (Azure AD)
  3. Database replication problems
  4. DDoS attacks (rare)
  5. Deployment bugs during updates
  6. Network routing issues

How Microsoft Responds

Communication channels:

Timeline:

  1. 0-15 min: Users report issues on Twitter
  2. 15-30 min: Microsoft acknowledges on status page
  3. 30-90 min: Updates posted every 30 min
  4. Resolution: Usually 2-6 hours for major outages

What to Do During Outages

1. Use Outlook on the web:

2. Use mobile app:

  • Outlook mobile might work when desktop fails
  • Different connection path to servers

3. Access via IMAP:

  • Configure email client with IMAP
  • Thunderbird, Apple Mail, etc.
  • Might work when Outlook doesn't

4. Switch to backup communication:

  • Teams (for internal communication)
  • Gmail (personal backup)
  • Slack/Discord (team communication)
  • Phone/SMS (critical communications)

5. Monitor status page:

6. Post-incident report:

  • Microsoft publishes Post-Incident Review (PIR)
  • Available in admin center 5-7 days after resolution
  • Explains root cause and remediation

Outlook Down Checklist

Follow these steps in order:

Step 1: Verify it's actually down

Step 2: Quick fixes (if Outlook is up)

  • Restart Outlook app (fully quit first)
  • Click Send/Receive All Folders (Ctrl+M)
  • Restart router
  • Disable VPN
  • Update Office to latest version
  • Test internet connection

Step 3: Network troubleshooting

  • Test connection: ping outlook.office365.com
  • Check firewall (allow Outlook, ports 443, 587, 993)
  • Allow Outlook in antivirus
  • Try Ethernet instead of WiFi
  • Try mobile hotspot to isolate issue

Step 4: Account troubleshooting

  • Test account settings (File → Account Settings)
  • Re-enter password if prompted
  • Clear credential cache (Credential Manager)
  • Check mailbox not full
  • Verify license active (if Microsoft 365)

Step 5: App troubleshooting

  • Start in Safe Mode (outlook.exe /safe)
  • Disable all add-ins
  • Clear Outlook cache (delete .ost file)
  • Run scanpst.exe (Inbox Repair Tool)
  • Create new Outlook profile

Step 6: Nuclear option

Prevent Future Issues

1. Keep Office Updated

Enable auto-updates:

  • File → Account → Update Options → Enable Updates

Why it matters:

  • Security patches
  • Bug fixes
  • Performance improvements
  • New features
  • Better Exchange Online compatibility

Check version regularly:

2. Enable Cached Exchange Mode

Recommended for better performance and offline access.

Enable Cached Exchange Mode:

  1. File → Account Settings → Account Settings
  2. Double-click email account
  3. ✅ "Use Cached Exchange Mode"
  4. Set sync slider (1-3 months recommended)
  5. OK, restart Outlook

Benefits:

  • Faster performance
  • Work offline
  • Reduces server load
  • Better sync reliability

Downside:

  • Uses local disk space
  • Initial sync takes time for large mailboxes

3. Regular Mailbox Maintenance

Prevent "mailbox full" and performance issues.

Weekly maintenance:

  • Empty Deleted Items folder
  • Archive old emails (>1 year)
  • Delete large attachments (save to OneDrive instead)
  • Clean up Junk Email folder

Use Mailbox Cleanup:

  1. File → Info → Mailbox Cleanup
  2. View Mailbox Size
  3. Find large items: "Find items larger than..."
  4. Empty Deleted Items
  5. View Conflicts size

Enable AutoArchive:

  1. File → Options → Advanced
  2. AutoArchive Settings
  3. ✅ Run AutoArchive every X days
  4. Set archive location
  5. Configure retention policy

4. Monitor Service Health Proactively

Don't wait for problems.

Set up alerts:

  • Microsoft 365 admin center → Service health → Preferences
  • ✅ Email me service health notifications
  • Use API Status Check for monitoring
  • Subscribe to @MSFT365Status

For IT teams:

  • Monitor Microsoft Graph API status
  • Set up automated health checks
  • Have incident response plan
  • Configure message center alerts

5. Implement Email Backup Strategy

Don't rely solely on cloud.

Backup options:

1. Export to PST regularly:

  • File → Open & Export → Import/Export
  • Export to a file → Outlook Data File (.pst)
  • Save to external drive

2. Use third-party backup:

  • Veeam Backup for Microsoft 365
  • AvePoint Cloud Backup
  • Barracuda Cloud-to-Cloud Backup

3. Enable Litigation Hold:

  • Preserves all emails permanently
  • Requires E3/E5 license
  • Contact admin to enable

4. Archive to personal account:

  • Auto-forward to Gmail (personal backup)
  • Only for non-confidential emails
  • Check company policy first

6. Optimize Outlook Performance

Faster Outlook = better experience.

Performance tips:

1. Limit sync duration:

  • File → Account Settings → Change
  • Use Cached Exchange Mode slider
  • Sync 3-6 months instead of "All"

2. Disable unnecessary add-ins:

  • File → Options → Add-ins
  • Disable unused add-ins
  • Especially old/unmaintained ones

3. Compact data files:

  • File → Account Settings → Data Files
  • Select file → Settings → Compact Now

4. Turn off Reading Pane:

  • View → Reading Pane → Off
  • Loads messages faster

5. Disable animations:

  • File → Options → Advanced
  • ❌ "Use animations in Outlook"

6. Optimize search:

  • File → Options → Search
  • Limit search scope to current mailbox
  • Rebuild index if search slow

Key Takeaways

Before assuming Outlook is down:

  1. ✅ Check Microsoft 365 Status
  2. ✅ Try Outlook on the web
  3. ✅ Test on mobile app
  4. ✅ Search Twitter for "Outlook down"

Common fixes:

  • Restart Outlook + router (fixes 50% of issues)
  • Force Send/Receive (Ctrl+M)
  • Update to latest Office version
  • Check firewall/antivirus settings
  • Create new Outlook profile (fixes 80% of persistent issues)

Sync issues:

  • Check account settings (test account)
  • Clear Outlook cache (delete .ost file)
  • Disable add-ins (Safe Mode)
  • Verify credentials not expired

If Outlook is actually down:

  • Monitor status.office.com
  • Use Outlook on the web as backup
  • Try mobile app
  • Usually resolved within 2-6 hours
  • Check admin center for tenant-specific issues

Prevent future issues:

  • Keep Office updated (enable auto-update)
  • Enable Cached Exchange Mode
  • Regular mailbox maintenance (archive, delete)
  • Monitor service health proactively
  • Implement backup strategy

For developers:

  • Monitor Microsoft Graph status
  • Implement retry logic for API calls
  • Use webhooks instead of polling
  • Check throttling limits
  • Enable SMTP AUTH in admin center

Remember: Most "Outlook down" issues are local profile corruption, network issues, or outdated app problems. Try the fixes in this guide before assuming Microsoft's servers are down.

Need real-time Outlook status monitoring? Track Microsoft 365 uptime with API Status Check - Get instant alerts when Outlook or Exchange Online goes down.

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