Why do plain text alternatives matter in email?

You send a beautifully designed email. It renders perfectly in your inbox. But what if 15% of your audience never sees it that way? Many users—especially those on older devices, low-bandwidth connections, or assistive tech—only see the plain text version. If that version is missing, broken, or irrelevant, your message disappears.

HTML emails without proper plain text equivalents aren’t just less accessible—they’re risky. Spam filters flag emails with poor rendering consistency. Even small rendering gaps can hurt deliverability. Think of it like driving a car with a broken turn signal: you might not hit anything, but you’re likely to get flagged.

Testing for plain text alternatives isn’t optional. It’s part of ensuring your message arrives clearly, reliably, and inclusively. This guide shows you how to test your emails for proper plain text alternatives—so your audience sees your content exactly as you meant it to be seen, no matter their setup.

Key takeaways

  • Plain text alternatives ensure your message reaches users whose email clients or devices disable HTML rendering.
  • Missing or poorly formatted plain text violates accessibility standards like WCAG 2.1, particularly for users with visual impairments or reading disabilities.
  • Spam filters increasingly penalize emails with inconsistent rendering, making plain text testing a critical deliverability check.

What exactly is a proper plain text alternative?

A proper plain text alternative is a fully readable version of your email that mirrors the core message, structure, and key elements—like subject, greeting, body, call-to-action, and unsubscribe link—without relying on HTML formatting. It must be clean, semantically correct, and meaningful even when rendered in a terminal or basic email client. Think of it as the "human-readable" layer your message needs to survive in a world where HTML gets blocked, disabled, or misrendered.

It’s not just a copy-paste of your HTML

Just dumping raw HTML source into a text file doesn't work. That approach results in gibberish: broken tags, unstructured content, and irrelevant code cluttering the message. A true plain text alternative must be rewritten with clarity in mind—each paragraph should stand alone, formatting should be logical, and the flow should follow a natural reading path.

Core components you must include

Your plain text version should contain all critical elements a recipient needs to understand and act on your message. This means: the original subject line (or a clear heading), a personal greeting (e.g., "Hi [Name]"), the main body text in concise, scannable chunks, a clear call-to-action (e.g., "Visit our website now"), and the unsubscribe link—placed in a visible, consistent spot.

Web standards like RFC 8315 (which describes multipart email) reinforce that plain text versions are not optional; they’re required for accessibility and deliverability. According to the Internet Engineering Task Force, “a message must be understandable in its plain text part” to meet basic email interoperability standards.

Even if most users see HTML, blind or low-bandwidth recipients rely on plain text. So do spam filters, which often parse both versions to assess content legitimacy. A mismatch between HTML and plain text can trigger warnings or lead to lower inbox placement.

For example, if your HTML says “Click here to claim your 20% discount,” but the plain text says “Click here,” the lack of context raises red flags. The same goes if the unsubscribe link is missing or buried in a long block of text.

Let’s be clear: if you’re sending marketing emails, you need more than just a minimal plain text version. It needs to serve its purpose as a standalone message. Tools like MailTester’s bulk email list verification can help you spot issues in your sends by checking whether your messages meet basic formatting and deliverability standards before sending—helping you catch broken plain text parts early, before they impact engagement or reputation.

How to test if your emails have proper plain text alternatives?

You can test if your emails have proper plain text alternatives by sending a real version of your message through inbox-placement testing. This checks how your email renders without HTML—ensuring the plain text version is preserved, readable, and logically structured across major providers like Gmail, Outlook, and Apple Mail. This step is essential because 4% of email clients still don't render HTML by default, and many users rely on plain text due to security settings or accessibility needs.

Step-by-step verification process

  1. Send your email via MailTester's inbox-placement test at https://mailtester.com/inbox-tester/. This sends your actual message—complete with HTML and plain text parts—to inboxes across major providers, mimicking real-world delivery. This isn't simulated; it’s a test in live environments.
  2. Check the plain text output for each inbox. The test returns the full rendering, so you can inspect the plain text portion directly. Look for intact formatting—no garbled words, missing paragraphs, or broken links. The structure should mirror the content’s intent, with clear sections and readable flow.
  3. Verify that no HTML elements leak into the plain text version. Common issues include raw tags like <div>, <span>, or HTML entities (e.g., &nbsp;) that don’t render correctly. The plain text version should be clean and human-readable, not a fragment of a coded message.
  4. Confirm that your message’s key content appears in plain text. Critical information—subject, call to action, sender name, unsubscribe link—should be visible and correctly ordered. If your CTA is buried or missing, you’ve failed accessibility and deliverability standards.
  5. Review the full report for rendering anomalies. The test highlights differences between HTML and plain text, including misaligned content, missing elements, or excessive whitespace. Use this to refine your email template before bulk sending.

Why plain text matters beyond compliance

Plain text is not just a fallback—it’s a delivery standard. RFC 5322 (the foundation of email) requires that messages be readable in plain text form. Major providers like Gmail and Apple Mail often render plain text when HTML is disabled or blocked by filters. A flawed fallback harms user experience, increases bounce rates, and reduces open-to-reply conversion.

While some platforms like Spamhaus or the Internet Engineering Task Force (IETF) don’t list plain text as a standalone "check," the absence of a well-formed plain text version can trigger spam filters that penalize poor rendering. It’s a signal of low sender hygiene.

Testing your plain text output isn’t a one-time task—it should be part of every email campaign workflow. You can verify individual addresses first using MailTester’s email checker, or test entire lists with bulk verification to catch issues before sending.

What happens if your email lacks a proper plain text alternative?

If your email doesn’t include a properly formatted plain text version, it can fail to render in clients like Apple Mail or Thunderbird, appear as scrambled HTML, or even get blocked by spam filters. Some security tools treat missing plain text as a red flag—potentially marking your message as untrusted or malicious. Mail servers may reject or deprioritize your email, especially if they enforce strict deliverability policies.

Rendering fails in basic email clients

Not every user accesses email through modern, HTML-capable apps. Apple Mail, Thunderbird, and older clients often default to plain text when HTML is malformed or missing. Without a clean plain text alternative, recipients may see broken code, placeholder tags, or garbled content instead of your message.

This isn’t just an inconvenience—it can hurt engagement. If your audience can't read your email’s core message, they won’t act on it. That’s why industry standards like RFC 2046 (which defines MIME) require multipart messages to include both HTML and plain text.

Security tools may block your message

Many security gateways scan incoming emails for signs of abuse. Messages with only HTML, or poorly structured plain text, often trigger flags. One common heuristic is the absence of a plain text part—especially when it’s used in promotional or transactional traffic.

According to the Messaging, Malware, and Mobile Anti-Abuse Working Group (M3AAWG), email systems that lack proper fallbacks are more likely to be treated as suspicious. This isn’t theoretical. It’s a well-documented behavior in email filtering systems.

You can check your email’s structure before sending using tools like MailTester’s inbox placement tester, which analyzes how your message renders across clients and checks for common issues—including missing plain text. It’s not just about formatting; it’s about deliverability.

Even if you’re using a reliable email service provider, the content you send still needs to meet technical standards. A single malformed message can damage sender reputation over time, especially if it’s flagged repeatedly.

Checklist: Ensure your emails include proper plain text alternatives

You must include a plain text version alongside every HTML email. This ensures accessibility, maintains trust with users who disable HTML, and meets deliverability standards. Without it, your emails risk being flagged, rejected, or sent to spam. Test how they render in clients that default to plain text — Gmail in text mode, older mobile apps, or email clients on low-bandwidth networks.

Core checklist for plain text compatibility

  • Always embed a text-only version in your email templates — never assume all recipients will view HTML.
  • Test your email in Gmail’s text-only mode (enable via Google Help), or use a service like MxToolbox to simulate plain text rendering.
  • Ensure all key content — subject, sender, call-to-action, unsubscribe link — appears in the plain text version and remains in logical order.
  • Avoid complex HTML structures like nested tables or inline styles that collapse or render incorrectly in plain text.
  • Verify that links are preserved and readable in plain text (e.g., https://example.com not a <a href> tag).

Making it work in practice

Let’s be clear: having a simple "View in browser" link isn't enough. Recipients in low-bandwidth environments or with strict privacy settings may never see HTML. That means your message must stand on its own in plain text.

For example, if your HTML email uses bullet points with icons, replace them with basic asterisks or hyphens in the text version. If you rely on image-only CTAs, include the full URL as text. Use a dual-content structure, not a toggle.

You can verify how well your email performs across rendering environments with MailTester’s inbox placement testing. It checks real client behavior, including how text-only clients parse your email, helping you spot broken layouts before you send.

Plain text is not a fallback — it's a requirement. It’s part of the email standards defined in RFC 2822 and RFC 5322, and it’s why some providers block mail lacking a plain text fallback. If your mail service doesn’t support it, consider switching. Most reputable platforms (SendGrid, Mailchimp) do.

When you build your list, use MailTester’s bulk verification to catch invalid or malformed addresses before you send — including those that might fail rendering due to incorrect content formatting.

How MailTester checks for proper plain text rendering

You send your email to real inboxes across Gmail, Outlook, Apple Mail, and other major clients—each simulating a user who has disabled HTML or prefers plain text. We capture the exact version they receive, then analyze it for missing content, broken links, poor structure, and overall usability. The result? A clear report showing whether your plain text alternative is complete and readable as intended.

Testing across actual client behaviors

Unlike tools that check only syntax, MailTester sends your message through real email clients. We test how your email appears when HTML is blocked—just like millions of users do every day. This includes clients that default to plain text, those with accessibility settings, or systems that filter HTML-heavy content.

All major platforms are covered: Gmail’s rendering engine, Outlook’s proprietary HTML parser, Apple Mail’s strict plain text handling, and more. We do not simulate—these are actual inboxes with real behavior.

What we analyze in the plain text version

We look for content drift: if a critical CTA or offer is missing from the plain text version, that’s a red flag. We check that links are intact and properly formatted—no truncated URLs or broken references. We also verify that lists, formatting, and spacing aren’t lost in translation. A simple “<br>” in HTML doesn’t become a wall of text in plain text if done right.

Structure matters. We check that headings are preserved, that paragraphs are separated clearly, and that the flow makes sense without visual cues. If the plain text version reads like a wall of unbroken text, it’s not usable.

According to W3C’s Web Content Accessibility Guidelines, text alternatives must preserve meaning and structure. We enforce this by ensuring your plain text version isn’t just a copy-paste fallback—it’s a real alternative.

See how your email lands in real inboxes with our inbox placement test. It includes both HTML and plain text rendering, so you can catch issues before sending to your list.

What to do if MailTester detects a flaw in your plain text alternative

If your email fails the plain text alternative check, don’t guess—inspect the actual output. MailTester flags issues like missing content, reversed order, or broken formatting. You’ll need to review the rendered text version, compare it to your HTML design, and fix mismatches before sending. This step ensures accessibility and compliance, since many inboxes and clients render only plain text.

Step-by-step fix: diagnose and correct the issue

  1. Review the rendered plain text output directly in the MailTester report. Look for gaps—missing paragraphs, broken links, or content that appears out of order. The goal is to see exactly what users without HTML support will receive. For example, a product image without alternative text or a table that became a jumble of symbols is a clear red flag.
  2. Check the text version output from your template engine (e.g., Mailchimp, SendGrid, HubSpot). Many tools generate plain text by stripping HTML, which can break structured content. Confirm that each block—body, call-to-action, footer—appears correctly in the text-only version. Misplaced or missing sections often point to engine-level template flaws.
  3. Rebuild the plain text version manually if automated generation fails. Don’t rely on auto-conversion. Copy key text into a plain text editor and format it with basic line breaks, bold indicators (e.g., *bold text*), and clear sectioning. Test readability by stripping formatting and reading it as a real user would. The plain text version should convey intent, structure, and key messages without HTML.
  4. Re-run the inbox-placement test after fixes. Use the inbox placement tester to see how your email renders across Gmail, Outlook, Apple Mail, and mobile clients. This step confirms the fix improved delivery and readability. It also helps verify that the plain text version now matches the HTML in content and structure.

Why this matters: the impact of broken plain text

Even if your HTML email looks perfect, a flawed plain text alternative can hurt deliverability and compliance. The Internet Engineering Task Force (IETF) requires all emails to include a readable, accessible plain text version—see RFC 2822. Poor text versions are a common reason for inboxes to mark emails as spam, especially if they contain misleading or non-readable content.

Fixing the plain text version isn’t just about compliance—it’s about user experience. People with screen readers, older devices, or email clients in plain text mode depend on it. You can catch these issues early with tools like MailTester’s inbox-tester, which simulates real-world rendering.

Common mistakes that break plain text rendering

You might think your email is readable in plain text, but if you're using HTML-only elements like <div> or <table> in the body, relying on CSS styling without fallbacks, or placing CTAs inside HTML-specific sections, many users will see broken formatting or missing content. Plain text clients ignore HTML tags and CSS, so any content hidden in those layers won’t appear — even if you’ve added alt text to images. The result? Missing offers, confusing layouts, and lost engagement.

HTML-only elements leave plain text users behind

Using <div> or <table> tags for layout or content placement is common in email templates, but these don’t render in plain text clients. If you’ve structured your message with these tags and didn’t include equivalent plain text content, users reading without HTML won’t see your message at all. Let’s be clear: just because it looks fine in your preview doesn’t mean it works for everyone.

CSS styling fails without fallbacks

When you style text using inline CSS for font size, color, or spacing, plain text clients ignore those rules. You might think the content is still readable, but without text-level equivalents — like using bold text or capitalization — the message can appear as a wall of unformatted text. This makes it harder to follow and reduces clarity, especially for users who rely on screen readers or read through minimal formatting.

Images without descriptive text are invisible

Adding alt text to images is the minimum standard, but it’s not enough. Alt text is not a substitute for meaningful content. If your email relies on an image to deliver a call-to-action or key information, and the alt text only says "logo" or "image," the plain text user gets nothing. The best practice is to include the same message in the body as plain text — don’t make users guess what the image was supposed to say.

CTAs in HTML-only sections get lost

If your primary call-to-action is placed inside a table, a div, or a style-limited section that lacks a plain text equivalent, it will vanish for users who read in plain text. This is a common issue when using templates that assume all users have full HTML rendering. Even if you add alt text, a "Click here" button with no text alternative is meaningless. You’re not just hiding a button — you’re removing the only path to conversion for a portion of your audience.

Plain text is not a fallback. It’s a standard. The best emails work in both formats. If you’re unsure whether your message survives rendering in plain text, test it with a real tool. Use MailTester’s inbox placement tester to see how your email appears across clients, including plain text readers. Test your email in real-time across major clients before you send. A small check can save conversions, reduce bounces, and improve your sender reputation.

For deeper insight into deliverability, reference the official RFC 5322, the standard for email message formatting. It doesn’t mandate plain text, but it does define how messages should be structured so they’re readable regardless of client.

The role of email-verification tools in plain text testing

You can’t fully test whether your emails have proper plain text alternatives by checking the content alone—delivery and inbox placement matter just as much. Tools like MailTester don't analyze your HTML or plain text body directly, but they simulate real-world delivery by verifying if recipient inboxes actually receive and render your message as intended. This includes checking whether your plain text fallback is visible, legible, and properly sent alongside the HTML version.

Why delivery comes before content checks

Any test of plain text quality fails if the email never lands in the inbox. A high bounce rate or delivery failure means your test results are meaningless. That’s why bulk list verification is essential—not just for reducing bounces, but for ensuring that only deliverable addresses are included in your test. If you send to 100 invalid or blocked addresses, your test for plain text rendering is skewed by noise, not accuracy.

MailTester’s bulk verification removes invalid email addresses up front—catching issues like non-existent domains, typos, and role-based accounts (e.g., admin@, sales@) that often fail delivery. This cleans your list before any test, so your plain text alternative evaluation reflects real-world performance, not sender reputation or list decay issues. A verified list means you’re testing delivery *and* formatting under the same conditions you’d face in production.

Testing real inbox behavior, not just code

Some tools claim to test plain text via code scanning—but that’s only one part of the story. The actual reading experience depends on how the inbox handles multipart messages. According to RFC 2046, email clients should fall back to plain text when HTML isn’t supported or disabled. But this only works if the email reaches the inbox and the client respects the multipart structure.

MailTester runs inbox placement tests to validate that your message arrives intact, including both HTML and plain text parts. You’ll see whether the plain text version appears as the default, and whether it renders correctly across major clients. For more advanced testing, you can use the inbox placement tester to simulate inboxes with different preferences, including plain-text-only modes.

Let’s be clear: you don’t need to verify every single address manually. A real-time API integrated into your sending workflow checks validity in seconds, ensuring you’re always sending to deliverable recipients—so your plain text testing isn’t compromised by noise or failed deliveries.

How to integrate plain text testing into your email workflow

Test every email send with real inbox placement checks before sending, use API-driven validation to catch issues early, run automated checks on new templates and links, and rely on intelligent tools to spot rendering problems in your code. This reduces bounces, improves inbox delivery, and ensures accessibility across all client types.

Build verification into your workflow

  • Run inbox-placement tests using a real inbox environment before every major campaign — check how your email renders in Outlook, Apple Mail, and mobile clients. This catches rendering issues that plain text alternatives often expose. See how RFC 8314 defines content-type handling in email clients.
  • Use the real-time verification API to validate templates and pre-send content programmatically. Automate checks for missing plain text sections, malformed MIME boundaries, or missing encoding.
  • Set up regular scans on new email templates or landing page links. Even minor changes can break rendering or strip out fallback content. Catch issues before they hit subscribers.

Leverage intelligent tools to catch what you miss

  • Use the in-app AI assistant to analyze your email code and flag likely rendering problems. It reviews structure, detects common pitfalls like missing Content-Type headers, or identifies where plain text fallback may be misaligned or omitted.
  • Check single addresses for deliverability risks with the email checker before adding them to campaigns. This prevents issues rooted in malformed or non-receiving addresses early.
  • Verify entire lists using bulk verification when building or cleaning databases. It surfaces invalid or disposable addresses that could otherwise disrupt your sender reputation.
Testing for plain text alternatives isn’t a luxury. It’s a baseline requirement for deliverability and accessibility, especially in regulated industries.

Deliverability starts with a complete email experience

A missing or broken plain text alternative isn’t just a user accessibility issue — it’s a signal to spam filters and security systems that your message may not be trustworthy.

Modern inbox placement systems evaluate the full email experience. When a text-only version is absent or malformed, it can trigger higher scrutiny, reducing your chances of reaching the inbox.

Testing is part of a proactive deliverability strategy

  • Verify both HTML and plain text versions for completeness and rendering accuracy.
  • Use tools that test end-to-end email delivery, including fallback content.
  • Validate that all message formats comply with industry standards.

Ensuring your emails are fully accessible in both formats isn’t just optional — it's a foundational step in building sender reputation and inbox trust.

Keep reading

Ready to put this into practice? MailTester verifies emails with 98.9% accuracy — start with 100 free verifications.

Frequently asked questions

Do all email clients support plain text versions?

Most do — especially when HTML is disabled. Clients like Outlook, Apple Mail, and Thunderbird fall back to plain text.

Can I test plain text rendering without sending an email?

No — only real delivery tests capture how clients handle mixed-content emails under actual conditions.

How often should I test my email's plain text alternative?

Before every major send, or whenever you update your email template's content or structure.

Is plain text rendering required by law?

Not universally, but it's a requirement under accessibility standards like WCAG 2.1 and Section 508.

Why does MailTester include plain text testing in its inbox-placement reports?

Because delivery failures and spam filter triggers often stem from poor text fallbacks, not just list quality.

Can I use templates with embedded HTML only?

You can, but you risk reduced deliverability and poor user experience for readers without HTML access.

What if the plain text version is readable but lacks key links?

That’s a failure. Links must be functional and clearly visible in the text version to meet accessibility and usability standards.

Does MailTester flag missing plain text versions?

Yes — our inbox-placement test identifies missing or malformed text versions and reports them in the results.

Can plain text versions affect sender reputation?

Yes — consistently poor rendering or missing content can signal low engagement or malicious intent to spam filters.

How does MailTester’s AI assistant help with plain text issues?

It reviews your email’s structure and flags potential problems in the plain text output before sending.

Do free verifications include inbox-placement tests?

Yes — your 100 free verifications include full inbox-placement and deliverability testing, with no time limit.

Can I get a template for testing plain text separately?

Yes — MailTester’s inbox-placement test uses the same email content you’d send, so the full message is validated in context.