From RFC5322, Internet Message Format: "Each line of characters MUST be no more than 998 characters, and SHOULD be no more than 78 characters, excluding the CRLF."

Subject-less?

Actually this a problem with most mail clients. They are terribly slow, even web based ones, for people who have multiple accounts, have a high email volume, and have to archive all their mail and have it easily accessible. Essentially the problem is most email clients suck, many terminal apps have been optimized for speed and thus many people with a ton of email use them, the culmination of all my mailboxes is about 22Gb of email! Outlook sucks at handling mailboxes over 5Gb same with most other clients, Gmail is ok at it but searching is a bit slow, and organization and control isn't that great. Gmail is also slow in usability compared to most clients like mutt or sup.

Not only that but HTML emails INCREASE mailbox size dramatically! Especially HTML signatures, because they generally use several different sizes/faces of font, contain images and may introduce "email backgrounds". In many cases the HTML markup of an email may be LARGER than the content of the email.

There's a difference between resisting progress and promoting simplicity.