I cannot send messages or reply to messages

Follow these steps in order:

1. Confirm internet connectivity
   • Open a browser (Microsoft Edge or Google Chrome).
   • Browse to http://www.microsoft.com or http://www.bing.com.
   • If these sites do not load, resolve the network issue first using the guidance in Fix network connection issues in Windows.
2. Manually sync Outlook
   • In Outlook, go to the View tab on the Ribbon.
   • Select the Sync button to force a manual sync.
   • Watch the status bar at the bottom of the message list to confirm that Outlook is syncing.
   • If using a third‑party account (Gmail, Yahoo, iCloud, generic POP/IMAP), note that the manual Sync button may not be available.
3. Check for password or app‑password issues
   • If the account password was changed on the email provider’s website, update it in Outlook as well.
   • For new Outlook:
     1. Select the icon next to the email account name.
     2. When the sign‑in prompt appears, select Continue.
     3. Enter the updated password and complete sign‑in.
   • If Outlook shows a message like Please create an app password for Outlook on your email provider's site:
     1. Sign in to the email provider’s site and generate an app password following their instructions.
     2. Copy that app password and paste it into Outlook when prompted for the account password.
4. Check antivirus and add‑ins (classic Outlook)
   • If using classic Outlook on Windows and an antivirus product that scans email, verify with the antivirus help desk that it is not blocking outgoing mail after detecting a virus.
   • Start Outlook in safe mode to rule out add‑ins:
     • Press the Windows key, type outlook.exe /safe, then press Enter.
     • If sending works in safe mode, create a new Outlook profile as described in Create an Outlook profile.
5. Repair Outlook and the Outlook profile (classic Outlook)
   • Repair the Outlook/Office installation using the steps in Repair an Office application.
   • If the issue persists, repair the Outlook profile or create a new one using Fix your Outlook email connection by repairing your profile.
6. Repair local Outlook data files (classic Outlook)
   • If using classic Outlook with a .pst file, run the Inbox Repair Tool (ScanPST) as described in Repair your Outlook personal folders file (.pst). This can fix data‑file issues that prevent sending.

If none of these steps resolve the issue, follow the broader guidance in Troubleshooting Outlook issues for more in‑depth diagnostics.

References:

• I can't send or receive messages in Outlook