Hello, thank you for reaching out to Microsoft Q&A.
- Are you able to Send E-mails?
- What is the exact error message the sender receives when they email you?
Send a test email from another one of your accounts to the affected email address. Check whether you receive any bounce-back (non-delivery) error messages. If you receive an error in the outbox, 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, or forwarded to another email address.
- Open any web browser (use incognito tab), Sign in with your Microsoft account here: 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)
Then, check your email Rules and Blocked senders lists.
(Select Settings > Mail > Junk Email > Blocked Sender lists)
Additionally, ensure you have enough mailbox storage space to send and receive emails.
Make your account more secure:
1. Protect your account with a Strong Password/ Reset your Microsoft account password.
Open an InPrivate/Incognito browser window and use the following link to reset your password: https://account.live.com/ResetPassword.aspx
2. Sign out of your account from all sessions.
Once the password reset is successful, sign in with your account here: https://account.live.com/proofs/Manage
Scroll down until you find Sign out everywhere. Select Sign out everywhere.
3. Enable two-step verification.
On the Security settings page, under Additional security, turn on Two-step verification. Make sure you have at least three security verification methods active.
After you have enabled these security protections, sign out of your account in the Outlook app and sign back in with your new password.