Notes on Plain Text vs. HTML Mail

Contra HTML mail

• Ecologically expensive due to increased size of messages
• High complexity

  • Harder to develop, hence more expensive
  • Handling more likely to break (e.g. Kaputte Zitate im Plain-Text von Gmail)
  • Less transparent; errors are harder to debug (for users and developers)
  • Higher hurdle for first time users (e.g. for composing newsletters)
• Security hazards (cf. security bug fixes of main mail programs such as Security Advisories for Thunderbird; cf. Efail: HTML Mails have no Security Concept and are to blame)
• Privacy hazards (e.g. HTML is used to track users)
• Some automated systems (e.g. mailing lists) do not accept HTML and will reject messages, or use only the alternative plain text part, or convert the HTML potentially causing formatting issues.
• Requires HTML aware software
• Double effort (HTML and text need to be formatted and checked)
• Little guarantee that HTML will be shown as intended
• More distractions when writing (e.g. font selectors, emoji buttons)
• Harder to write (formatting takes more time)
• "Angry fruit salad": Every user chooses a different font in a different color and different size.

Pro HTML mail

• Ability to format and style the message content
• Ability to create "rich" content (graphs, tables, ...)
• Ability to use semantic markup (e.g. to mark text as preformatted)

Contra plain text mail

• Text wrapping issues if lines are hard-wrapped (not format=flowed) (e.g. on mobile devices with small screens)
• Text formatted for fixed width fonts might get distorted
• Some content is better sent as attachment (e.g. illustrations)

Pro plain text mail

• Easy, small, ecologically friendly (compared to HTML mail)
• Text is shown by all devices and programs
• Accessibility as good as it gets

Criteria to consider

• False positive spam: It is unclear whether HTML mails are more likely to be falsely categorized as spam.
• Accessibility: It is unclear whether HTML mails that include alternative plain text parts are less accessible, for instance for text to speech conversion.

References

• Wikipedia: HTML email
• Hanno Böck: Efail: HTML Mails have no Security Concept and are to blame
• Jason Rodriguez: HTML Email and Accessibility | CSS-Tricks Recommended, extensive article published 2017-11-22.
• LUGA.at thread "Plain Text vs. HTML-Mails" October + November 2017.
• Niti Shah (HubSpot Marketing): Plain Text vs. HTML Emails: Which Is Better? [New Data] Originally published 2015-07-27, updated 2017-10-29.
• Jonathan Corbet (LWN.net): The trouble with text-only email Published 2017-10-12. With many interesting comments
• Bratus S, Shubina A: The only safe email is text-only email. The Conversation, 2017-09-11. Also available from Scientific American.
• mkln.org: Wie man E-Mails schreibt Published 2017-02-24.
• Greg Kogan: Don't Design Your Emails Published 2016-06-28.
• AWeber Email Marketing: Plain Text vs HTML Email: What Reaches the Inbox in 2014? Published 2014-04-22.
• For historical reference:

  • Discussion about HTML in e-mail Last revision 1998-05-22.
  • The Ascii Ribbon Campaign official homepage from around 2000 or even earlier