Hello, thank you for reaching out to Microsoft Q&A.
- Are you able to send emails normally? Is this a Personal or Work account?
- Are you trying to access all of your emails using the new Outlook for Windows desktop app? Do you experience the same issue when viewing your emails on Outlook.com in a web browser? https://outlook.live.com/
- Have you checked your Junk or Spam folders to see if all incoming emails are being automatically delivered there?
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Check Your Microsoft Account Storage.
- Open Outlook Web.
- Sign in with your account.
- Go to Settings > Accounts > Storage.
- Expand the Microsoft Storage and E-mail storage section.
- See if you have enough space to send or receive emails.
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Send a Test Email.
Send a test email from another one of your accounts to the affected email address. Check whether you receive any bounce-back error messages in the Outbox. If you receive an error, please share the complete error message here.
If the email is sent successfully, then please check your email forwarding rules and blocked senders list, and verify whether the messages have been routed to another folder, such as Junk or Spam.
Email forwarding rules: https://outlook.live.com/mail/0/options/mail/forwarding
(Click Do not forward if your emails are being forwarded to another address)
Let me know if you still need more help.