As a Mailgun customer, I can unfortunately confirm this. A lot of our clients are having problems getting mails delivered in hotmail mailboxes. This started some weeks ago, and we haven't seen any improvement since. It is getting to a point that we're working on migrating to something else right now.
I'm sorry we let you down. If it's not too late, I'd love to get to the bottom of this today. Can you share details with me? josh [at] mailgun [dot] com
