Re: This has been happening for a long time now
Same. Run my own mail server. Last week is was blocked for email to hotmail addresses but NOT outlook addresses due to part of my ISP's network being on their block list! Fill in the MS form. MS respond that there's no reason why mail should not be deliverable from my IP and ask for the error message (which I supplied back at the start when filling their form). Replied and copied the error message AGAIN. Within 24 hours normal service to hotmail addresses resumed as they had "mitigated the IP".