Ads and tracking

I’ve been reading Paul’s article about Proton and the new outlook and how the new outlook is harvesting data. Is it the outlook app that is the problem here or is it using Microsoft / Google for email ?

I presume this is so whether or not an outlook.com email address is being accessed ? Is it also true for Microsoft 365 accounts ( as many businesses use).

Does anyone have any recommendations for alternative email providers ( apart from Proton which is clearly an option) ?