I want to leave gmail behind

The more I try to leave it the harder it gets, the problem is I like using external clients such as Thunderbird and mutt and things like Tutanota and ProtonMail won't support such clients directly.

Yes, there is the proton bridge but I keep hearing it's buggy (especially on Linux which I'm also using), I also want to use things like git-send-email and that requires SMTP.

Paying for an email provider or self-hosting isn't realistic for me at the moment …

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