Microsoft 365 email not syncing in Outlook? Test the mailbox online first.

1. Visit outlook.office.com and sign in with the affected Microsoft 365 account.
2. Open the Inbox and look for the recent messages you expect.
3. Send a message to your own address. Verify that it reaches Sent Items and arrives in the Inbox.
4. Compare those test messages with classic Outlook on the computer.

Online pass: you can sign in, open the mailbox, see recent mail, send the message and receive the test or reply. Choose the passed button even if the computer has not caught up.

Online failure: sign-in or mailbox access fails, an error appears, mail is missing, sending fails or remains pending, a delivery failure arrives, no test/reply arrives, or mailbox storage is full. Choose the failed button for step 2.

Classic Outlook has a File tab. Use the classic Windows app for the computer steps; the menus in new Outlook are different.

1. Ask your administrator to sign in at admin.microsoft.com. If you do not have administrator access, ask them or call us.
2. Under Health → Service health, review Exchange Online for an incident affecting the organisation.
3. Review the subscription licences under Billing → Licenses.
4. Under Users → Active users, open the affected user. Review Licenses and apps and the Mail details, and have the administrator confirm that the Exchange Online mailbox is available.

Leave licence changes to your administrator or Call IT Mate. Do not remove a licence or assign it again as a troubleshooting step. After the administrator addresses the issue, repeat step 1 before continuing on the computer.

1. Open the affected folder in classic Outlook. Look for Filter applied at the lower left of the window.
2. Before comparing mail, open View → View Settings → Filter. Select Clear All to remove the view filter, then confirm the open dialogs with OK.
3. Read the connection status along the bottom of Outlook. If it shows a connected Microsoft Exchange status, use Send/Receive → Send/Receive All Folders and check for the test mail.
4. If it says Working Offline, select Send/Receive → Work Offline once so the button is no longer highlighted. Then run Send/Receive All Folders and check the status again.
5. For Disconnected or Trying to connect, try Send/Receive All Folders. If mail still does not sync, continue to step 4 before making a new profile.

A connected label is useful, but the test email still needs to arrive. Use the syncing button only when the messages are appearing; otherwise choose the button for mail that still is not syncing.

1. Check the Outbox in the current profile. Open each waiting message in its own window.
2. For each message, select File → Save As. Choose your Windows Desktop, enter a file name and save the message file. If a message cannot be opened or saved, ask us for help before proceeding.
3. Keep these files for reopening and sending once the replacement profile works. The new profile will not recover mail that never reached Microsoft 365.
4. Exit Outlook and allow it a moment to finish closing.
5. Use Ctrl + Shift + Esc to open Task Manager. If Microsoft Outlook or OUTLOOK.EXE is still running, select it and choose End task.

Proceed only after the unsent messages have been saved and Outlook has stopped. Keep the existing profile; adding another one does not itself delete it.

1. Open the Start menu, search for Control Panel and open it.
2. Set View by to Small icons.
3. Open Mail (Microsoft Outlook) and select Show Profiles.
4. Select Add, name the profile Microsoft 365 New Profile and select OK.

The account setup window opens next. Keep the existing profile; adding a new one does not delete it.

1. Enter the mailbox email address in the account setup window and choose Connect.
2. Complete the Microsoft sign-in prompts, including your password and verification when requested.
3. Allow Outlook to find the account settings. Complete the wizard with Finish when offered.

If setup fails, involve the administrator or Call IT Mate. Do not continue to the sync checks with an account that has not been added successfully.

1. Back in the Mail window, select Show Profiles.
2. Select Always use this profile and choose Microsoft 365 New Profile.
3. Select Apply, then OK.
4. Open Outlook.

Don't remove the original profile.

1. Keep Outlook running and leave the computer connected to the internet while it syncs.
2. Check for a connected Microsoft Exchange status, then choose Send/Receive → Send/Receive All Folders.
3. Look for the recent messages you saw online. Send a test email and find its copy in Sent Items.
4. Reply using another account and confirm that the reply reaches Outlook.
5. Once sending and receiving work, reopen the message files saved from the old Outbox and send the emails that still need to go.

There is no fixed wait time in this guide. If the mailbox does not connect or the tests keep failing, ask us for help.

1. Confirm new messages, replies and outgoing mail appear in the correct folders.
2. Check Sent Items, Deleted Items and the other folders you use.
3. Try the calendar, contacts, search and attachments.
4. Check that your rules behave as expected.
5. If your work uses shared mailboxes or delegated calendars, check access to them too.