Hi Arif,
Please follow the steps below to do some checking to troubleshoot the issue.
1. Log in to the OWA through http://mail.office365.com/ with your account.
2. Click Options on the top right side of the page and click See All Options…
3. Click Organize E-Mail tab and select Inbox Rules. Please make sure no listed inbox rules are related to Mark Message as Read.
Please let me know the result of checking for further troubleshooting. However, could you please tell me what plan of Office 365 you are using right now?
Thanks,
Yang Yu