Same with the post here: https://answers.microsoft.com/en-us/msoffice/forum/all/unable-to-receive-email-on-office-365-through... but no definite answer to this.
Issue with Inbound emails.
Mx records are pointing to barracuda > exchange online.
Some emails are getting stuck in barracuda having the error below:
550 5.4.1 All recipient addresses rejected : Access denied. AS
Spoke with Barracuda but, they said no issues on their end as it's being received by the spam filter but when trying to send it to EXO, it's getting rejected.