E-mail is Not HTML, Web Pages Aren't a Form of E-mail
In 2025 it is still worth repeating the obvious: E-mail is an inherently text-only message transmission protocol and it may come with attachments, however some believe that sending "plain text" HTML (raw message body with hypertext) or adding HTML attachments to E-mails is OK. Some people/firms add spyware to their messages that way, e.g. invisible pixels, logos, overloaded hyperlinks or HotLinking to tracking domains.
It's not only causing bloat (backup impediment) among other things; it also introduces security risk, which the lousy EFF can then spin as a problem in PGP ("e-fail"), in turn discouraging the use of End-To-End Encryption (E2EE) in favour of "apps" on back-doored devices remotely controlled at all times by some hostile entities.
There's some new promotional 'article' from Barracuda (ITWire became somewhat of a commercial spamfarm; Sam Varghese became inactive nearly a year ago) saying that a vast proportion of E-mail attachments are "malicious". If they were to include SPAM and marketing in the "malicious" category (unwanted stuff basically), then the attachments deemed bad/unwanted would likely be as high as 60% if not 90%, mostly depending on the recipients surveyed. In my own inbox I'd say about 80% of attachments are unwanted. Some pose a security risk, some is just extra bloat attached to SPAM.
HTML E-mails can themselves be regarded as a form of attachment because the HTML parts piggyback what ought to have been plain text. Due to webmail or "web mail", which we covered last month, the notion of E-mail being HTML "by default" became increasingly normalised. And apropos web mail, as an associate remains us, always use "plain text, it was good enough for Shakespeare". █