Not really. In the Marketo example I mentioned, the sending host was generic and not dedicated to Microsoft workloads. Many of the bureaux I have mentioned are significant senders of grey mail; bulk based on a previous commercial relationship rather than the traditional dubious pharma spam or the latterly more commonplace criminal phishing, but still nonetheless unsolicited and capable of overwhelming a mailbox if unmanaged. The EXO scores I mentioned therefore came as no surprise.
Take a look at the headers of samples of your quarantined Microsoft traffic. See what the Forefront scores are. Take the sending IP address and put it through any online reputation service that will tell you who owns it. I predict that it won't be Microsoft.
It is also worth noting that typically Junk Mail would go to Junk folders rather than the hosted quarantine. Your organisation may have a rather stiff threat policy on Junk, there may be a somewhat excessive mail flow rule or if your colleagues do not have the same problem, you may want to double-check your own Outlook settings.
