Check the status bar at the bottom of classic Outlook first; if it shows Working Offline, Disconnected, or Trying to connect, restore the connection before troubleshooting search or individual folders.
1. Restore Outlook’s connection
- In Outlook, select Send/Receive.
- Select Work Offline once to switch back online. A shaded Work Offline button means Outlook is offline.
- Select Send/Receive All Folders.
- Confirm that the bottom status changes to Connected and try sending a small test message without an attachment.
Classic Outlook cannot send or receive while disconnected. Microsoft does not document the exclamation overlay alone as identifying one specific error, so the text on the status bar is the more useful indicator.^1^
Also check:
- Open a website to verify that Windows has Internet access.
- If the password for the mailbox was recently changed, complete any sign-in prompt in Outlook.
- Open Outbox and remove or edit the oldest stuck message, particularly if it has an attachment larger than 20 MB; one oversized message can block later messages.^2^
2. Determine whether the problem is Outlook or the mailbox
Sign in to the business mailbox through Outlook on the web and check whether you can:
- Open Sent Items and Drafts
- Search the mailbox
- Send a test message
If all of those work online, the mailbox is available and the problem is local to classic Outlook—most commonly its profile, cached data, or search index. If they also fail online, contact the Microsoft 365 administrator or mail provider because repairing the Windows Outlook client will not resolve a server/account problem. This web-versus-desktop comparison is also Microsoft’s recommended way to distinguish a local Sent Items issue.^3^
3. Repair or replace the Outlook profile
If webmail works but classic Outlook still cannot send or display folders:
- In Outlook, select File > Account Settings > Account Settings.
- On the Email tab, select the affected account.
- Select Repair, complete the prompts, and restart Outlook.^4^
If Repair is unavailable or does not fix it, test a new profile:
- Exit Outlook.
- Open Windows Control Panel > Mail > Show Profiles.
- Select Add, enter a temporary profile name, and add the business account.
- Select Prompt for a profile to be used, then start Outlook with the new profile.
- Allow synchronization to complete before testing Sent Items, Drafts, sending, and search.
If the new profile works, set it as the default; the old profile is the affected component.^5^
4. Fix search only after mail and folders synchronize
If sending and folders work again but search still returns no results:
- Select Outlook’s Search box.
- Select Search Tools > Indexing Status.
- If the remaining-item count does not decrease after five minutes, close Outlook.
- Open Windows Control Panel > Indexing Options.
- Confirm Microsoft Outlook is an included location.
- Select Advanced > Rebuild, then reopen Outlook and allow indexing to finish.
Also confirm the Windows Search service is running: open services.msc, open Windows Search, set it to Automatic (Delayed Start), and select Start if necessary.^5^
If the warning remains and neither profile repair nor a new profile works, run Microsoft’s Classic Outlook connectivity or authentication troubleshooter.^6^
References
- [Classic Outlook](https://support.microsoft.com/outlook/getstarted/how-to-work-offline-in-outlook-for-windows#status-messages-in-classic-outlook)
- [Classic Outlook](https://support.microsoft.com/outlook/i-can-t-send-or-receive-messages-in-outlook#make-sure-you're-connected-to-the-internet)
- Sent Folder Issue - Microsoft Q&A
- Fix your Outlook email connection by repairing your profile
- [Classic Outlook](https://support.microsoft.com/outlook/troubleshooting-outlook-search-issues#classic-outlook-search-returns-no-results)
- Classic Outlook troubleshooters | Microsoft Support