Initially I was cancelling these but I've now realized it's possible to uncheck the report_spam@hotmail report, check the 'user report' option under it, then fill in the abuse address for the ISP who's in charge of that particular IP address.
You can find this by looking in the headers for the point at which a non-Microsoft server has handed off the messaging to a Microsoft server and running a whois on the IP address of that hand-off server. From your link above this is the relevant section:
Received: from mail1.listingbookmail.com (74.202.231.63) by
HE1EUR02FT053.mail.protection.outlook.com (10.152.11.109) with Microsoft SMTP
Doing a whois 74.202.231.63 | grep Abuse gives us the following results:
OrgAbuseHandle: TWTAD-ARIN
OrgAbuseName: tw telecom Abuse Desk
OrgAbusePhone: +1-800-829-0420 OrgAbuseEmail: abuse@level3.com
OrgAbuseRef: https://whois.arin.net/rest/poc/TWTAD-ARIN
RAbuseHandle: TWTAD-ARIN
RAbuseName: tw telecom Abuse Desk
RAbusePhone: +1-800-829-0420
RAbuseEmail: abuse@level3.com
RAbuseRef: https://whois.arin.net/rest/poc/TWTAD-ARIN
network:Abuse-Contact;I:abuse@twtelecom.net
So then you fill in abuse@level3.com into the blank 'user' field and submit that, instead.