It seems that Microsoft blocks every IP address on the Internet by default, except those for which mail server administrators like NinerNet have to beg repeatedly to have removed. Our requests keep being ignored, despite the fact that we are members of both their Smart Network Data Service (SNDS) and their Junk Mail Reporting Program (JMRP), but we will keep trying.
Currently this means that we route Microsoft’s main domains — hotmail.com, outlook.com, msn.com and live.com — through our relay server which is not blacklisted as it pre-dates their aggressive blocking practices. However, if you send email to a non-Microsoft domain hosted by Outlook/Office365, you will almost certainly receive a bounce message that looks like this (if the domain you sent to hosted by Microsoft is “exampledomain.com”):
Remote-MTA: dns; exampledomain-com.mail.protection.outlook.com
Diagnostic-Code: smtp; 550 5.7.606 Access denied, banned sending IP
[178.62.195.26]. To request removal from this list please visit
https://sender.office.com/ and follow the directions. For more information
please go to http://go.microsoft.com/fwlink/?LinkID=526655 (AS16012609)
