Hello, thank you for reaching out to Microsoft Q&A.
Are you able to send emails normally? Do outgoing emails work as expected?
Could you please provide the exact error message you receive when you send emails to other recipients?
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 or if the email gets stuck 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)
Additionally, check that you have enough mailbox storage space available to send and receive emails.