Microsoft Outlook can not connect to the server

If Classic Outlook shows Working Offline, select Send/Receive → Work Offline once to reconnect, then select Send/Receive All Folders and check whether new mail arrives.^1^

If Outlook still says Disconnected or Trying to connect

1. Test the mailbox outside Outlook
   • Open your email provider’s website and sign in to webmail.
   • Send yourself a test message from another account.
   • If webmail also cannot receive it, the issue is with the mailbox or mail provider; contact the provider.
   • If webmail receives it, the server and mailbox are operating, so continue with the desktop-client steps below.^1^
2. Check whether the password changed
   • If the mailbox password was recently changed through the provider’s website, update the stored credentials in Outlook.
   • If Outlook requests an app password, obtain one from the email provider and use it instead of the normal password.^2^
3. For POP or IMAP accounts, verify server settings
   • Go to File → Account Settings → Account Settings.
   • Select the affected account, then choose Change or Server Settings.
   • Compare the incoming server, outgoing server, ports, encryption type, username, and authentication settings with the provider’s current settings.^3^
   • Do not guess the values; obtain them from the email provider.
4. Repair the Outlook profile
   • Go to File → Account Settings → Account Settings.
   • On the Email tab, select the account and choose Repair, if that option is available.
   • Restart Outlook and test Send/Receive.

If repair does not restore synchronization

Create a new Outlook profile rather than immediately deleting the existing one:

1. Close Outlook.
2. Open Windows Control Panel → Mail → Show Profiles.
3. Select Add, create a profile, and add the email account.
4. Start Outlook with the new profile and test receiving mail.

Microsoft recommends a new profile when Classic Outlook remains disconnected; if the new profile also fails, remove and re-add the account in that new profile.^1^

For an Exchange or Microsoft 365 account where webmail works but Classic Outlook does not, rebuilding the local .ost cache is another option:

1. Close Outlook completely.
2. Press Windows+R.
3. Enter %LOCALAPPDATA%\Microsoft\Outlook\.
4. Locate the .ost associated with the affected mailbox and rename it, for example to mailbox.ost.old.
5. Reopen Outlook and allow it to synchronize a new local copy.^4^

Renaming is safer than deleting because the original file remains available. Do not use this procedure for a .pst file, which can contain locally stored mail.

If none of these steps works, provide the email provider/account type—Microsoft 365/Exchange, Outlook.com, Gmail, Yahoo, or another POP/IMAP provider—and the exact Send/Receive error code. Codes such as 0x800CCC0E, 0x800CCC0F, and 0x80042108 identify different connection paths.^2^

References

1. Classic Outlook
2. Classic Outlook
3. Troubleshoot Outlook email setup | Microsoft Support
4. Can send email but cannot receive email. - Microsoft Q&A