Which is defeated by the default settings in Thunderbird, the email client used in most GNU/Linux distributions. This is not the case with the default setting in proprietary email clients, such as those in Microsoft and Apple products since they want to cater first to marketers and large corporations who are typically very heavy users of html in email. The security of individuals in the case of Microsoft and Apple is secondary to marketing and DRM to the benefit of large corporations, if it is a consideration at all.

Your link explains well the convoluted process needed to disable this invasion of privacy in most proprietary email clients. I stand by my position the first line of defense for privacy is to say no to the likes of Microsoft and Apple. Monero builds upon a reasonable privacy framework, but it is not a substitute for taking basic measures to protect one's privacy.