Does including a plain text version of an email improve deliverability and conversion rates?
Matthew Whittaker
Co-founder & CTO, Suped
Published 25 Apr 2025
Updated 15 Aug 2025
8 min read
For years, email marketers have debated the importance of including a plain text version alongside their HTML emails. Does it truly impact how often your emails land in the inbox? And beyond deliverability, can it actually sway recipients to take action?
The conventional wisdom has long been to always include a plain text alternative. This practice stems from a time when not all email clients could render HTML, or when security settings were much more restrictive. While email technology has evolved, the question of its impact on deliverability and conversion rates remains relevant for today's senders.
I often see marketers focusing heavily on intricate HTML designs, sometimes overlooking the simpler, underlying plain text component. However, this seemingly basic element can play a nuanced role in how your emails perform.
The impact on deliverability
When you send an email with both HTML and plain text versions, you're creating what's known as a multipart/alternative MIME type. This allows the recipient's email client to choose the most appropriate version to display. For instance, if a client cannot render HTML, it will default to the plain text. But does its mere existence improve email deliverability even if the HTML is viewed?
Including a plain text version can reduce the likelihood of your email being flagged as spam because it provides a reliable fallback for mailbox providers and security filters. These systems can inspect the plain text version, ensuring consistency with the HTML and checking for malicious content that might be hidden in complex HTML code. This dual-format approach signals legitimacy and good sending practices.
Furthermore, a well-constructed plain text part acts as a safeguard. If there are issues rendering your HTML, perhaps due to client limitations, network problems, or strict security settings, the plain text version ensures your message is still fully readable. This prevents a blank or broken email from reaching the recipient, which could otherwise negatively impact your sender reputation and overall deliverability.
It also plays a crucial role in accessibility for users who rely on screen readers. Screen readers often process the plain text version for optimal performance, ensuring your message is conveyed clearly to a broader audience.
Ensuring proper implementation
The key isn't just to include a plain text version, but to ensure it is properly formatted. Many Email Service Providers (ESPs) automatically generate a plain text version by stripping HTML tags, but this often results in a messy, unreadable mess. Manually crafting this version ensures it retains clarity and crucial information.
Example of a multipart/alternative email structureemail
Content-Type: multipart/alternative;
boundary="--_=========PlaintextHTMLBoundary_=========--"
----_=========PlaintextHTMLBoundary_=========--
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
This is the plain text version of your email.
Visit our website: example.com/link
----_=========PlaintextHTMLBoundary_=========--
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
<html>
<body>
<p>This is the HTML version of your email.</p>
<a href=3D"http://example.com/link">Visit our website</a>
</body>
</html>
----_=========PlaintextHTMLBoundary_=========--
Conversion rates and user experience
While the impact of a plain text version on direct deliverability might be subtle in modern email environments, its effect on conversion rates can be more pronounced. This isn't always about the plain text version being viewed, but rather what its presence (or absence) signals about your sending practices.
Some marketers have reported surprising lifts in conversion rates when including a custom plain text version, even when analytics showed no direct clicks on plain text specific links. This suggests that the mere existence of a well-formed plain text version can indirectly contribute to better engagement, possibly by influencing how email clients and spam filters perceive the email's legitimacy and overall quality. When an email is fully compliant and well-structured, it tends to perform better.
A crucial factor is how email clients render your HTML. If your HTML version has rendering issues, even minor ones, or if the recipient's email client struggles with complex designs, they might switch to the plain text version, or simply discard the email. A clean plain text alternative ensures the message is never lost, maintaining a positive user experience.
Additionally, a plain text email can feel more personal and less like a mass-marketing message. This can foster a stronger connection with the recipient, encouraging higher engagement and potentially leading to better conversion rates. Research from HubSpot indicates that simpler HTML emails, and even plain text emails, can outperform visually rich emails in terms of open and click-through rates.
Technical alignment and link integrity
One area where the plain text version becomes particularly critical is in how email sending platforms handle link tracking and rewriting. Many ESPs modify links in HTML emails for click tracking, but they might not apply the same modifications to the plain text version. This can create a mismatch between the HTML and plain text URLs.
If a mailbox provider or a spam filter (or even a vigilant recipient) detects significant discrepancies in the URLs between the HTML and plain text parts, it could raise a red flag. This inconsistency might be interpreted as an attempt to hide malicious links, potentially leading to your email being flagged as spam or directed to the junk folder.
It's essential to ensure that any tracking parameters or URL modifications are consistently applied across both versions of your email, or that your plain text version contains the direct, clean links if rewriting is only applied to HTML. Always test how your HTML and plain text emails are processed by your ESP.
While UTM parameters themselves are unlikely to trigger spam filters, having them consistently applied across both email parts is crucial for accurate tracking and to avoid any flags related to mismatched content.
HTML vs. Plain text: when to choose what
Deciding between HTML and plain text involves weighing visual appeal against deliverability and perceived authenticity. Here’s a comparison to guide your strategy:
HTML emails
Visuals: Offers rich formatting, images, videos, and branding elements.
Tracking: More robust tracking capabilities for opens and clicks.
Use cases: Newsletters, promotional campaigns, and elaborate marketing messages.
Plain text emails
Simplicity: Minimal formatting, focusing solely on content.
Deliverability: Less likely to trigger spam filters due to complexity.
Use cases: Cold outreach, transactional emails, and highly personalized messages.
While many campaigns benefit from visually appealing HTML, there are instances where a plain text-only approach (or ensuring a robust plain text alternative is present) can be more effective. For example, cold outreach or transactional emails often perform better as plain text because they mimic a one-on-one communication, increasing perceived authenticity.
Regardless of your primary format, always strive for content parity between your HTML and plain text versions. Inconsistent content or links can be a significant red flag for email filters, impacting your email's blocklist status and overall deliverability (or inbox placement).
Key takeaways
While HTML emails offer rich design capabilities, the humble plain text version remains a critical component of successful email marketing. Its presence enhances deliverability by providing a robust fallback and signals legitimacy to spam filters. Furthermore, a well-crafted plain text email can boost conversion rates by improving user experience across diverse email clients and fostering a more personal connection with recipients.
Prioritizing the proper formation of both your HTML and plain text versions, and ensuring their content aligns, is a foundational best practice for any sender aiming for optimal inbox placement and engagement. Remember, true deliverability success isn't just about avoiding the spam folder, it's about consistently reaching the primary inbox and driving action.
Views from the trenches
Best practices
Always include a carefully crafted plain text version that accurately reflects your HTML content, especially for crucial links and calls to action.
Regularly test how your emails render across different email clients, paying attention to how the plain text version appears.
Ensure that any link tracking or rewriting performed by your ESP is consistent between your HTML and plain text parts to avoid discrepancies.
Consider using plain text-only emails for specific campaigns, such as cold outreach or transactional messages, where a personal tone is desired.
Common pitfalls
Relying solely on auto-generated plain text versions from your ESP, which often lack proper formatting and can contain broken content.
Having mismatched links or content between your HTML and plain text versions, which can trigger spam filters and hurt deliverability.
Neglecting to test the plain text version of your emails, assuming it will always render correctly or won't be seen by recipients.
Over-optimizing HTML emails with excessive images or complex code, which might lead to rendering issues that push recipients to view plain text.
Expert tips
Focus on the consistency of the message and links between HTML and plain text versions. Any discrepancy can be a red flag for filters.
If you see a significant conversion lift from plain text, investigate if there are HTML rendering issues specific to certain mailbox providers or email clients.
For B2C audiences, simple HTML or even plain text can often perform better due to the perception of a more personal communication.
Monitor your deliverability metrics, including bounce and complaint rates, and analyze performance by ISP to identify any patterns related to email format.
Expert view
Expert from Email Geeks says that the impact on deliverability from a well-formed plain text email is likely not directly noticeable.
2020-06-23 - Email Geeks
Expert view
Expert from Email Geeks says that a plain text message removes many potential issues that filters might find problematic, so it generally won't hurt deliverability.
2020-06-23 - Email Geeks
Conclusion
The plain text version of your email is more than just a fallback; it's a fundamental part of a robust email strategy. While it might not always be the version your recipients see, its existence and proper formation contribute significantly to both email deliverability and overall campaign effectiveness.
By ensuring your plain text version is thoughtfully created and consistent with its HTML counterpart, you enhance accessibility, reduce spam flags (or blocklist inclusion), and provide a seamless experience for all your subscribers. This meticulous approach can lead to improved engagement and, ultimately, better conversion rates for your email marketing efforts. Never underestimate the power of simplicity and compliance in the complex world of email.
