Hi Joseph,
I've had the same issue that started a year ago. Eventually they removed the subnet, but it was blocked again a week later.
It seems to me they import a third party block list containing my subnet, which re-blocks it shortly after removal, and they won't whitelist. They wouldn't tell me the source (nor the reason).
I've repeated the remove/block cycle a few times and then just gave up and renumbered my mail servers. They don't seem to care. At all.
Your mileage may vary though. If you do get to a solution I'd appreciate hearing about it :) Good luck!
We are getting this messages when sending emails from our domain. We've
submitted tickets, but haven't received a response yet. Anyone have any
insights?
550 5.7.1 Unfortunately, messages from [1.1.1.1] weren't sent. Please
contact your Internet service provider since part of their network is on
our block list (S3140). You can also refer your provider to
http://mail.live.com/mail/troubleshooting.aspx#errors. [
AM5EUR03FT014.eop-EUR03.prod.protection.outlook.com]
It's our own address and everything on the Microsoft site says we are clean
with no issues.