Image-only emails and missing plain-text version

What it means

A well-built email usually contains two versions of the same message, packed together:

• an HTML version, with layout, colors and images;
• a plain-text version, just the words and links, for simple mail apps and for filters.

Two common mistakes trigger spam filters:

• Image-only emails: the whole message is one picture (a flyer, a scanned poster) with little or no real text. Spammers do this to hide words from filters, so filters distrust it.
• No plain-text version: the email only has HTML. It is not forbidden, but it is a small negative signal, and it often goes with other bad habits.

Why it matters

• SpamAssassin and similar filters add points for emails with little text and big images, or with HTML only.
• Many mail apps block images by default: your reader sees an empty email with a "show images" button.
• Screen readers cannot read text inside an image, so the email is not accessible.

How to check

Delivmail checks this for you in two ways:

• Send a test email: on the home page (/), copy your unique test address, send it a normal email from the mailbox you want to check, then open the report. The SpamAssassin section lists rules such as HTML_IMAGE_ONLY_*, HTML_IMAGE_RATIO_* or MIME_HTML_ONLY when they apply, with the points each one adds.
• Look at the raw source of your email: a plain-text part appears as Content-Type: text/plain next to text/html.

How to fix it

1. Write your message as real text. Put the title, the key information and the call to action in HTML text, not inside a picture.
2. Keep a balance. There is no magic ratio, but aim for clearly more text than image area. A few short paragraphs around each image is a good habit.
3. Add alt text to every image. In HTML this is the alt attribute, for example alt="Summer sale: 20% off". It shows when images are blocked.
4. Turn on the plain-text version.
   • Newsletter tools (Mailchimp, Brevo, and others) usually generate it automatically; check that it is enabled and readable.
   • In code, most libraries accept both a text and an html body. Fill in both.
5. Host images properly. Use images from your own domain or your email tool, not from a random free host that may be blacklisted.
6. Do not send a flyer as an attachment only. A PDF or image attachment with an empty body looks even worse. Write the message in the email, and link to the file if needed.
7. Keep the HTML clean. Code pasted from Word or a website builder can be huge and broken. Use your email tool's editor or a tested template.

Example of a good structure

Logo (with alt text)
Title in text
Two or three short paragraphs
One image (with alt text)
A clear button: "See the offer"
Footer: who you are, why they receive it, unsubscribe link

Check that it is fixed

Send the new version to a fresh Delivmail test address. The image and HTML-only rules should be gone from the SpamAssassin section, and your spam score should drop. Also open the email in your own mailbox with images turned off: it should still make sense.