Why can't I send messages on outlook?

Check the status bar at the bottom of classic Outlook first; if it says Working Offline, Disconnected, or Trying to connect, select Send/Receive → Work Offline to reconnect, then reopen the message and select Send or Send/Receive.^1^

If Outlook shows that it is connected

1. Test a small new message
   • Send a message to yourself with no attachment.
   • If it sends, an existing message is probably blocking the Outbox.
2. Clear the oldest message from the Outbox
   • Select Send/Receive → Work Offline.
   • Open Outbox and find the oldest message.
   • Delete it, or move it to Drafts and remove or reduce its attachment.
   • Microsoft notes that an attachment larger than 20 MB can block that message and messages queued behind it.
   • Select Send/Receive → Work Offline again to return online, then choose Send All.^2^
3. Check whether sending works through webmail
   • Sign in through your email provider’s website and send a test message.
   • If webmail also cannot send, the issue is likely with the account or email service rather than the Outlook desktop application.
   • For a work or school Microsoft 365 account, ask the administrator to check Microsoft 365 admin center → Health → Service health for an active Exchange Online incident.^3^
   • If webmail sends successfully, continue with the local Outlook checks below.

Check authentication and add-ins

• Password recently changed: Outlook may still hold the previous password. Update the stored Outlook credentials when prompted; the password itself must first be changed through the email provider or administrator.^4^
• Test Outlook without add-ins:
  1. Close Outlook.
  2. Press the Windows key, type outlook.exe /safe, and press Enter.
  3. Send a test message.
  If sending works in Safe Mode, an add-in is interfering. Microsoft recommends creating a new Outlook profile as the next corrective action.^1^

Run the Microsoft troubleshooter

If sending still fails, open the Windows Get Help app and run the relevant classic Outlook diagnostic:

• Search Outlook password problem for authentication failures.
• Run the Classic Outlook connectivity troubleshooter for intermittent connection problems.
• Run Classic Outlook advanced diagnostics to generate a configuration report.

These troubleshooters require Windows 10 or later, must run on the affected PC, and do not support new Outlook for Windows.^5^

If none of these resolves it, record the exact error text or code shown under Send/Receive. That code—especially an SMTP or authentication error—will determine whether the account settings, Outlook profile, antivirus email scanning, or email provider needs attention.

References

1. [Classic Outlook](https://support.microsoft.com/outlook/i-can-t-send-or-receive-messages-in-outlook#make-sure-you're-connected-to-the-internet)
2. Fix messages that are stuck in the Outbox
3. How to check Microsoft 365 service health
4. Troubleshoot Outlook email setup | Microsoft Support
5. Classic Outlook troubleshooters | Microsoft Support