Managing personal Outlook.com account settings, security, and privacy
Hi M,
I will help you out with this issue. With 75% storage being free, the email delivery should be smooth. Could you send an email from one of your other accounts to this problematic account and let me know if you receive any bounce-back message? Our next steps are based on the same.
Additionally, I hope you cleared out your Deleted Items folder as well, which is a must.
I look forward to hearing from you to get the results of the troubleshooting.