Cant send email to hotmail accounts from my business domain

28. September 2013 · Write a comment · Categories: Hotmail, Outlook.com · Tags: , ,
All of a sudden I can't send email to my hotmail account from my business domain, which is on my safe list AND
I have been doing for the past decade !!

Here is the return message:

This message was created automatically by mail delivery software.
A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:
  *** Email address is removed for privacy ***
    (ultimately generated from *** Email address is removed for privacy ***)
    SMTP error from remote mail server after end of data:
    host mx1.hotmail.com [65.55.37.120]: 550 5.7.0 (COL0-MC4-F13) Message could not
be delivered. Please ensure the message is RFC 5322 compliant.