I have a Hotmail account that I use for unimportant things--i.e., where I am required to create an account in order to access a service but I know I don't ever want to get mail from them. So, of course, I get a lot of spam on that account.
One big host offender is salesforce.com. Of course, the reports go to abuse#salesforce.com@devnull.spamcop.net
Before reading here and realizing that reports sent to abuse@saleforce.com just went into a black hole, I was forwarding messages to them as attachments. I'd done so with some regularity.
When I did so the other day I got a server error from outlook.com; thinking there was a glitch I tried again. Same problem. I checked my settings and tried a third time, and this time I received an email from Outlook member services--addressed to me, using the name I gave for my account profile, saying "We noticed some unusual activity in your Outlook.com account. To help protect you, we've temporarily blocked your account. ... Someone may have used your account to send out a lot of junk emails or something else that violates our Terms of Service."
I checked through the email, looking at every embedded link and they all seemed legit--the "verify your account" link was
https://account.live.com/reputationcheck?ru=https://outlook.live.com/owa/
I'm no expert but that looks valid, and indeed I couldn't otherwise log into my account.
So... Microsoft has no problem delivering Salesforce spam to me (by the busload) but nabs me for reporting it.