my domain is black listed
Here is the response from the IT department at the intended recipient.
Ok these messages were bounced
because the sending IP address was on a “RBL” or “Registered Black List.”
So this goes back to whoever he is hosting “@dgsboulder.com” through.
That hosting company’s Email
server is on a “Registered Black List.”
Until the hosting company fixes the problem, Mimecast will never allow email through at that address.