Why would Gmail's market share correlate with the number of emails sent? 99% of the 300bn sent daily will originate from bulk senders. Thats not Gmail.

I was responding to the part of OP's comment that alleges that Gmail is only big for personal email, and there's not a lot of that being sent. Gmail is clearly massive for enterprise email. I'm also not sure why this wouldn't correspond to market share in number of emails sent. All of those enterprises using Gmail are sending tons of emails internally.

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?).

FWIW, I've worked at two companies in my career so far, both could be described as tech unicorns turned public in the last decade, and both used G-Suite for all enterprise use-cases where applicable. Absolutely no adoption of MSFT products. That being said it also means I'm somewhat in the SV company bubble and I'm not sure how this picture looks throughout the industry.

Same. But I got a glimpse when I spent some time working at an established east coast company how much Microsoft is used for absolutely everything. I hadn't even heard of SharePoint but it is a whole massive universe unto itself.

Microsoft is huge for legacy companies. It integrates really well now with Office and while it was worse a few years back, it definitely seems to have improved now.

Among my cohort (20s-30s), I'd say it's 99% gmail. Is there something equally hegemonic for West Europe? A lot of my german friends use GMX but I don't see as much from other countries.

For personal email of people in The Netherlands that I know it's a mix of Gmail, hotmail.com (so Outlook.com, but old accounts) and ISP-provided email. Older people being disproportionately more likely to use their ISP, and younger people being more likely to use Gmail. The Hotmail accounts all seem to be from the time that MSN Messenger was incredibly popular, forming essentially the first social network. Those people are in their mid-20s. I'm not sure about the overall distribution.

London based here, my company is on G suit as well.