Hello Marvin Oco,
I'm copying this solution from another Microsoft blog:
source: https://answers.microsoft.com/en-us/msoffice/forum/msoffice_outlook-mso_winother-mso_o365b/550-54300...
Problem fixed after searching the error in Google.
1. Account was hacked. Probably when I was using an open WIFI to do work outside the office.
2. Hacker simply FORWARDED my emails to the gmail account.
3. Found the fix here. https://community.spiceworks.com/topic/1970153-office-365-strange-non-delivery-report
4. Microsoft description of the fix here - https://blogs.technet.microsoft.com/office365security/how-to-fix-a-compromised-hacked-microsoft-offi...
5. Logged in to 365 account and found the hacker had entered a gmail account and selected forward in the checkbox.
6. My IT spec says it will take 1 to 72 hours to fizzle out.
7. Waiting for results as of 8-11-17.
I hope that can help you.
