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...and make sure that all of the recipients / people sending you email do that too.
That's their problem, not yours. This is a universal issue with encrypted communications. If any party is compromised, the communications are compromised. This is no different from e.g. someone getting their computer pwned with malware.
You are right, however in this case the potential malware equivalent is pretty aggressive and doesn't need user interaction if they're running old software. Attacks need to be targeted of course though.
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