Yes this was resolved.
My companies website was hosted in a hosting centre with other sites on the same server. Another website on the server became compromised which resulted in the servers IP address being added to SPAM databases. Our website url www.domainname.com was in turn added to FOPEs database as the IP address resolved to the IP (exactly how FOPEs database is updated is still a mystery). All our outbound email had an HTML disclaimer appended which contained our web URL and was therefore blocked.
FOPEs ridiculous suggestion was to remove our web URL from all emails! They eventually removed www.domainname.com from the database and mail started to flow again. I contacted all SPAM databases we were listed against to have us delisted and we have no more problems.
I have also moved our website internally so we can control the security etc.
Our support provider maintained that I had caused this issue with the HTML disclaimer despite them detailing exactly how to add it. The root cause of our issue was the web server but it was FOPEs database that was the cause on the Office 365 side and not the disclaimer. Even if the disclaimer was removed the email would still have been blocked should 'www.domainname.com' appear anywhere in the mail i.e. an address block.
Regards
Simon...