NDR - Exchange - returned '550 5.4.300 Message expired - even if message was received

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-message-expired/4d0a6242-1234-4abd-af45-dc12216511b2?auth=1

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-office-365-account/

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.