There is some sort of problem when Outlook.com (or live.com as this account is) email users send to my mail server.  I just sent myself a test and, within 5 seconds, Outlook.com popped up with a DSN failure message.  I am able to send to gmail successfully.  Clients and partners who use outlook.com, though, are having trouble sending me email.

Meanwhile, no Microsoft mail server tries to connect to my mail server, so I'm seeing a DSN failure when delivery isn't even attempted.

What can I do to help resolve this?