Email Content and Deliverability

Content matters less than your reputation and list quality, but it still matters at the margin. A clean template will not save a bad list, and a quirky template will not sink a healthy program. Content decides outcomes mostly at the edges: clipped messages, image-only emails, and links to flagged domains.

Where Content Ranks

Inbox providers weigh signals roughly in this order: sender reputation, recipient engagement, authentication, then content. Complaints and bounces from a stale list outweigh anything in your template.

That said, content problems compound. A clipped email hides your unsubscribe link, which raises complaints, which hurts reputation. Fix the content issues below so they never become reputation issues.

Gmail Clipping at 102KB

Gmail truncates messages whose HTML exceeds 102KB and shows a "View entire message" link. Clipping causes real damage:

• Your unsubscribe link is usually at the bottom, so it gets hidden. Recipients who cannot find it click "Report spam" instead.
• The open tracking pixel often sits near the end of the HTML, so opens go uncounted and your metrics look worse than reality.
• Recipients rarely click through to the full message, so anything below the clip goes unread.

The 102KB limit applies to the HTML source, not images. Bloat usually comes from drag-and-drop editor output, inline CSS repeated per element, pasted content from Word or Google Docs, and very long messages.

Keep templates lean. Trim unused sections, avoid pasting from word processors, and send yourself a test in Gmail. If you see "View entire message" at the bottom, cut weight before sending.

Image-to-Text Balance

Image-only emails are a spam signal. Spammers use single large images to hide text from filters, so filters treat the pattern with suspicion.

Image-heavy emails also break in practice:

• Many clients block images by default, so the recipient sees an empty message.
• Screen readers get nothing to read.
• Text in images cannot be searched, copied, or resized.

Keep meaningful text in HTML. A reasonable target is that the email still makes sense with every image blocked. Add descriptive alt text to images that carry information. If Gmail hides your images with a warning, see Gmail Image Warnings.

Link Hygiene

Links are one of the most scrutinized parts of an email:

• Do not use public URL shorteners like bit.ly. They hide destinations and are heavily abused by spammers.
• Use one consistent branded tracking domain. Bento rewrites links through it, and a stable domain builds link reputation over time. See Open and Click Tracking.
• Do not link to flagged or low-reputation domains. One bad third-party link can trigger warnings on the whole message.
• Make visible link text match the destination. Mismatches look like phishing.

If Gmail shows a suspicious link warning, pause the campaign and follow Gmail Link Warnings.

The Promotions Tab Is Not Spam

Landing in Gmail's Promotions tab is deliverability success. The message reached the inbox. Tab placement is Gmail categorization based on content and sender patterns, not a reputation judgment.

Do not try to trick the tab system by disguising marketing as personal mail. Recipients who expected a promotion and got a fake-personal email complain more, and complaints are the metric that actually hurts. Many engaged subscribers check Promotions deliberately when they want offers.

Spend the effort on engagement instead. Gmail moves mail from senders a specific recipient consistently opens.

Plain-Text Part

Include a plain-text part alongside your HTML. Multipart messages are how legitimate mail clients send email, so a missing or mismatched text part is a weak spam signal. The text part also serves recipients on watches, screen readers, and clients with HTML disabled.

Keep the plain-text content equivalent to the HTML content. A text part that says something different from the HTML is a classic spam pattern.

Attachments

Avoid attachments in bulk email entirely. Attachments are a primary malware vector, so filters treat bulk mail with attachments harshly, and many corporate gateways strip or quarantine them.

Host the file instead and link to it. A PDF on your website behind a normal link delivers the same content without the filtering risk, and you get click tracking on it.

Transactional one-to-one mail, like an invoice to a single customer, is a different situation. But for broadcasts and automations, use hosted links.

The Spam Trigger Word Myth

Lists of forbidden words like "free" or "discount" are mostly outdated. Modern filters weigh sender reputation and recipient engagement far more than isolated words. Legitimate brands say "free shipping" in the inbox every day.

What still hurts:

• ALL CAPS subject lines.
• Excessive punctuation, like "!!!" or strings of emoji.
• Deceptive subjects that do not match the body. "RE:" on a first contact, fake forwards, false urgency. These are also illegal under CAN-SPAM.
• Heavy obfuscation like "F R E E" or "v1agra"-style spelling, which is itself a spam pattern.

Write subjects that honestly describe the email. The recipient deciding "I want to read this" is the signal that matters.

Rendering and Accessibility

Clean, accessible markup is a trust signal. Broken rendering reads as careless or fake, and sloppy HTML correlates with spam in filter models. Basics:

• Use semantic structure with real heading elements and lists.
• Set alt text on meaningful images.
• Keep contrast readable and font sizes at 14px or larger for body text.
• Avoid invisible text and tiny fonts. Hidden content is a classic spam technique and filters look for it.
• Test in Gmail, Outlook, and Apple Mail before big sends. Outlook on Windows uses Word's rendering engine and breaks layouts the others handle fine.

Preheader Text

The preheader is the snippet shown after the subject line in the inbox list. If you do not set one, clients pull the first text they find, which is often "View in browser" or alt text.

Use the preheader to extend the subject with a second hook, not repeat it. Keep it under about 90 characters so it survives truncation on mobile. A deliberate subject plus preheader pair raises opens, and opens feed the engagement signals that drive placement.

For guidance on keeping promotional content out of transactional mail, see Marketing vs Transactional.