Switch to a paid service that doesn't depend on your data or on ads for revenue and survival.
I would mainly recommend posteo.de because of what the company stands for and its cheap pricing. Other options are runbox.com and mailbox.org. All these providers support IMAP too. So you can use any email client on any platform, or the web interface, to access email.
Protonmail, recommended by some others here, doesn't support IMAP for free accounts (so you can't take your mail out easily if you want to move elsewhere). For paid accounts, it has a "bridge" software that needs to be installed and running. This is available only on Windows and Mac. For Linux, the FAQ [1] still says at multiple places that it'll be available in "early 2018", while we're already nearing the fourth calendar quarter of 2018.
