my outlook is not working not receiving the mails and not sending the mails

Use the following checks 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 open, fix the network first using the guidance in Fix network connection issues in Windows.
2. Check Outlook connection status (classic Outlook for Windows)
   • Look at the bottom status bar in Outlook.
   • If it shows Disconnected, Working Offline, or Trying to connect…, Outlook is not connected to the mail server.
   • Go to the Send/Receive tab on the ribbon.
   • In the Preferences group, select Work Offline once to toggle back online.
   • Then choose Send/Receive or open and resend any messages stuck in the Outbox.
3. Manually sync (where available)
   • On the View tab, select the Sync button.
   • Watch the status message at the bottom of the message list to confirm Outlook is syncing.
4. Check for large or stuck messages
   • Open the Outbox folder.
   • Open the oldest stuck message.
   • If it has large attachments (for example, over 20 MB), remove or reduce them, or replace them with a link.
   • Save and send again, then try Send/Receive.
5. If the password was recently changed
   • If the email account password was changed on the provider’s website, update it in Outlook as well.
   • For new Outlook: select the icon next to the account name, choose Continue when prompted to sign in, and enter the new password.
   • If prompted to create an app password (for providers that require it), generate the app password on the provider’s site and use that in Outlook instead of the normal password.
6. Check antivirus and add-ins (classic Outlook)
   • Some antivirus products block email when they detect issues. If email stopped after an antivirus alert, follow the antivirus guidance or contact its help desk.
   • Start Outlook in safe mode to rule out add-ins:
     • Press the Windows key, type outlook.exe /safe, and press Enter.
     • If mail works in safe mode, create a new Outlook profile and reconfigure the account.
7. Repair Outlook and the Outlook profile (classic Outlook)
   • If problems persist, repair the Office/Outlook installation using the Repair an Office application steps.
   • If still not working, repair or recreate the Outlook profile using the Fix your Outlook email connection by repairing your profile steps.

If the issue is with Outlook for Mac, additionally verify:

• SMTP server is not blocked by a firewall; if needed, get an alternative SMTP server from the ISP or admin and enter it under Tools → Accounts → Outgoing server.
• Username, password, SSL, and port settings are correct in Tools → Accounts.
• Any required proxy settings are configured in macOS System Settings.
• The mail server is online by confirming with the email provider or admin.

If using POP/IMAP and mail suddenly stopped, confirm the correct ports (for example, POP port changes like 993 to 995 as required by the provider) and reconfigure the account if needed.

References:

• I can't send or receive messages in Outlook
• I can't send or receive messages with Outlook for Mac
• Outlook has stopped receiving messages but will send them - Microsoft Q&A
• Why am I not able to receive emails which I used to on my outlook mac. I can send emails without any issues. - Microsoft Q&A
• Outlook is using a temporary email and I cannot receive emails - Microsoft Q&A