First, I doubt you would get someone to change the hotmail filters. It's not like they added a manual rule. It works on autopilot. The spamfilter learns that such message is bad. Not even the Microsoft guys really know how it decides that. And even if the ip address was blocked, the technicians would just be allowed to "mitigate" the ip, and are not allowed to deviate from the runbook.
Second, the migration to mailman3 probably changed them enough so they "lost" a lot of the reputation it gained through the years. So if may have learnt that a message with certain wikimedia headers was ok, but mm3 emails are different enough they don't hit.
Third, mailman
is sending spam messages to the list owners. Those are requested, but they are being sent, so hotmail does have a point.
Do not mark them as spam, even if it is a spam sent to <list>-
owner@list.wikimedia.org, you
want to receive them, not to make hotmail learn that email sent by
lists.wikimedia.org is spam.
Mails blocked to the list and sent to the list owners are problematic (and spammy) enough that I think mailman should offern an option not to include the full email not passed to the list, but only the subject. But that'd be a feature request.
In the end, if you are a list admin, you have requested to receive them, even if they are spammy. You should be able to configure your mail for that. However, you may be using a provider which doesn't allow that kind of flexibility.
By the way, gmail is marking me the previous mails of this list from Leon Haanstra as: "This message was not sent to Spam because of a filter you created." (they are not always obeying these filters ☹, but I am glad they at least allow them). This may be related to gmail considering list mail flow more spammy than usual, or simply because it's a
yahoo.com email address and thus it fails the silly DMARC policy they added.
Regards