How plain text and HTML email differ
An HTML email is a small web page delivered to an inbox: headings, colours, buttons, images and a layout that the mail client renders. A plain text email is exactly what the name says — characters, line breaks, and nothing else. No fonts, no buttons, no images, and links shown as the full address rather than as words you can click through.
In practice most campaigns are not one or the other. Email platforms send both parts inside the same message, a structure called multipart alternative, and the receiving client chooses which to display. That is why the plain text version still exists even when nobody ever looks at it, and why it is worth writing rather than leaving as an auto-generated dump of the HTML.
Why the choice matters
Format changes what you can measure and what you can ask for. Open tracking works by loading a tiny image, so a message displayed as plain text records no open at all — one reason open rate is a softer number than it looks. Buttons, product grids and branded headers only exist in the HTML part.
Format also changes how the message reads. A designed template announces itself as marketing before a word is read, which is right for a promotion and wrong for a one-to-one follow-up. A message that looks like it came from a person invites a reply; a message that looks like a poster invites a click or a delete. Neither is better in general — they are different jobs.
Where the choice goes wrong
The most persistent mistake is treating plain text as a deliverability trick. Filters judge the sending domain, its authentication and how recipients behave, not whether a message carries styling. Stripping the design from a campaign that people were happy to receive does not rescue a sender whose real problem is a stale list or an unauthenticated domain.
The opposite mistake is a template that is all image and no text, which collapses when images are blocked and gives filters nothing to read. Ignoring the plain text part is the quiet third: platforms will generate one automatically, and the result is often a wall of raw addresses and stray formatting that looks careless to anyone who sees it.
How to act on it
Match the format to the purpose. Newsletters, offers and anything with products belong in a well-built HTML template. Sales follow-ups, personal check-ins and short operational notes usually work better as text or as very light HTML that reads like typing rather than design.
Whichever you choose, keep the real message in words. Write the plain text version yourself so it stands on its own, and build HTML that still makes sense when images are blocked. On a patchy mobile connection, which is how much of Nepal reads email, a light template with real text arrives usable while a heavy one is still loading.