Which countries are you thinking about? Honestly haven't seen a company in the EU self hosting email for probably 15 years, and I used to run the email server at a company.
Self-hosted mail servers are not common anywhere. Smaller providers are more common in some places. Small provider isn't the same as self-hosted; neither is enterprise.
There are still countless exchange servers running in the default enterprise MS setup. Perhaps not for long since MS nudges people into their cloud, but they are still fairly common.