Office 365 Message Loop

[foofighterjim]

Very strange issue today. One of my users has tried to send an email to another user at the same domain, the email has not arrived.

 

Since trying to send this message the sender has been unable to send any other messages to anyone! The recipient seems to be unaffected. I have looked at the message trace logs and this email seems to be sending every minute but the status is always none. I have done the same report on the recipients account and I get the same message. Now I am stuck as I have checked the senders outbox and there is nothing, I have also looked in the sent items and again nothing.

 

I really do not know what to try next; I have never seen this before.

[foofighterjim]