Very interesting! Looks like my perspective is very Western Europe-centric, where the data matches what I expected. Gmail is bigger than I expected in the US, and also in Eastern Europe.

I do wonder what "market share" means here, and how the domains are selected. The massive market share of GoDaddy seems off, especially since from their website they seem to be reselling Microsoft Office 365, but could be explained by default email MX records on domains registered there (do they do that?).