Let's check. I just sent their support an email to ask for all personal data they have on me (I'm living in the EU, and have Swiss citizenship). I will update in this thread once I have an answer, and if I don't have one then that will be a good reason to write a blog article...

Regarding the IMAP support, I don't see how it's an issue that they provide it to their paid tier. ProtonMail is a paid service, with an option to have limited free accounts.