Plain text or HTML, and why cold email leans plain

The moment a cold email looks like a marketing email, it is treated like one, by the filter and by the reader. Plain text is not a limitation here, it is the disguise that makes cold outreach look like what it should be: a person writing to a person.

Cold email is not marketing email

Designed HTML emails, with images, banners and buttons, are built for opted-in marketing audiences. Cold outreach is trying to look like an individual reaching out, and design breaks that illusion instantly.

A plain-looking email matches the pretext of a personal message, which is exactly what makes it credible to a stranger.

HTML weight hurts deliverability

Images, tracking pixels and multiple links are among the signals spam filters weigh, and heavy HTML looks like bulk marketing. Plain or near-plain email is lighter and reads as personal, which helps it reach the inbox. This is the same logic behind a minimal signature and dropping tracking pixels.

Design lowers trust from a stranger

A polished template from an unknown sender reads as a campaign, and campaigns from strangers get deleted. A plain note reads as a real person who might actually want a reply.

The absence of design is doing work: it signals that this was written, not blasted.

Light formatting is fine

Plain does not mean ugly or unstructured. A little formatting, short paragraphs, the occasional line break, is fine and aids readability. What to avoid is the newsletter look: images, big buttons, columns, brand headers. Keep it to what a person would naturally type in a normal email.

What plain text means technically

"Plain text" gets used loosely, and the distinction is worth being precise about, because the two meanings have different consequences.

A true text/plain message carries no markup at all: no bold, no hyperlinks, no styling. Most sending platforms instead send multipart messages that include both a text part and an HTML part, and the client displays whichever it prefers. That is fine. The problem was never the presence of an HTML part, it was what teams put inside it.

A cold email whose HTML part contains one paragraph tag per paragraph and nothing else renders identically to a plain note and behaves like one. A cold email whose HTML part contains a table layout, a hosted logo, a background colour, three utm-tagged links and a 1x1 pixel behaves like a newsletter no matter what the copy says. Judge the email by what is in the markup, not by which checkbox the platform offers.

The same email, twice

Take an offer to a warehouse operations manager. Version A opens with a 600-pixel banner carrying the sender's logo, sets the body in a brand typeface at 15px, and ends with an orange "Book Your Free Consultation" button above a four-line signature block with social icons.

Version B is four short paragraphs of default text, one plain sentence asking whether a fifteen-minute call next week makes sense, and a signature of name, company and phone number.

Version A announces, before a single word is read, that it was sent to a list. Version B leaves the reader no way to tell whether they were the only recipient, which is exactly the position you want them in. The reply to version B also feels ordinary to send, because nothing about the message frames it as a marketing interaction requiring a marketing response. That framing difference is the substance of cold email is not marketing.

Where HTML still earns its place

None of this makes designed email bad. It makes it wrong for this one job. HTML earns its keep once permission exists:

• Newsletters to subscribers, where the reader opted in and expects a designed format.
• Product and release announcements to existing customers, where screenshots carry real information.
• Event invitations to a known audience, where dates, agendas and a booking button are the content.
• Transactional messages such as receipts and confirmations, where structure aids comprehension.

The dividing line is not aesthetic taste, it is whether the recipient asked to hear from you. Cold outreach sits on the wrong side of that line, so it borrows the conventions of personal correspondence instead.

Formatting mistakes that cost replies

• Multiple links in a first email. Every link is another signal for a filter to weigh and another decision for the reader. Fix: one link at most, or none at all in the first message.
• Pasting from a word processor. Copied text drags in inline styles, odd fonts and stray span tags. Fix: paste as plain text, then format inside the sending tool.
• Coloured or oversized type. Nobody writes a colleague in 18px teal. Fix: leave the defaults alone.
• A signature that outweighs the message. Logos, banners, legal blocks and social icons undo the plain look in one block. Fix: three lines, text only.
• Long unbroken paragraphs. Plain does not mean dense, and a wall of text on a phone gets abandoned. Fix: two or three sentences per paragraph, as covered in length and formatting.
• Emoji in the subject line. They read as promotional and sit alongside other filter signals, which is territory covered in spam words and filters.

Checking it before the campaign goes out

Run four checks on the first email of any new sequence:

1. Send it to yourself at a Gmail, an Outlook and a corporate address, then read all three on a phone.
2. View the source of the received message and count the tags. If it needs scrolling, it is too heavy.
3. Check the text-only rendering, since some corporate clients strip HTML by default and the message must still make sense.
4. Read it aloud. If it sounds like copy rather than a person talking, the formatting was never the real problem.

These checks take ten minutes once per sequence and catch most of what damages inbox placement. The wider set of controls sits in the deliverability guide.

The rule of thumb

If it looks like something a colleague could have typed to you, it is right. If it looks like it came from a marketing automation platform, it is wrong. Cold email leans plain because plain is what reads as personal, and personal is what gets answered.