"I don't think Microsoft look on you as a customer. Customers are OEMs who ship Windows installed on computers."
Strange as it may sound, but Microsoft have an area of their website divided into sections for various products, mostly software - called A Shop.
You can buy products directly from Micosoft through the shop and I'm not refering to the likes of X Box games.
Very handy for buying Microsoft 365 licences especially if you multiple email domains without having to buy complete licences for each. Unlike buying from somewhere like GoDaddu.
That is precisely how I purchased the subscription licence foteh the specific Outlook.com services that I'm using and have the issues with.
I'm pretty sure that giving them the money in return for Microsoft providing goods and/or services makes a customer of theirs