Hotmail bouncing email

[nanog at phaze.org (Greg Estabrooks)]

Is anyone  else out there getting reports of hotmail randomly bouncing 
emails with just a message of "failed"?

Over the last 2 weeks we've had a dozens of complaints of hosting 
customers spanning dozens of domains not receiving emails from hotmail 
users.  Checking our logs shows the messages were never even attempted 
to be delivered and all forwarded in bounce messages literally just say 
"Delivery failed", yet we are still happily processing thousands of 
other emails from hotmail everyday.

Now I'm wondering if this is restricted to us in someway or part of a 
larger problem.