Summary
Including a well-formed plain text version in your emails can indirectly improve deliverability and, in some cases, significantly boost conversion rates, even if recipients primarily view the HTML version. While direct, noticeable deliverability improvements from plain text alone are often minor, its presence mitigates risks associated with complex HTML and enhances accessibility for various email clients and users. The true benefit often lies in avoiding negative deliverability impacts and catering to diverse viewing preferences, which can cumulatively lead to better engagement metrics and ultimately higher conversions.
Key findings
- Risk mitigation: A plain text alternative reduces the chances of an email being flagged by spam filters due to issues with complex HTML code or missing images, which might otherwise cause delivery problems. This is especially important for ensuring your messages don't land in a recipient's spam or junk folder, which can be a common email deliverability issue.
- Conversion lift: Some A/B tests have shown a notable increase in conversion rates for emails that include a custom plain text version, even when the plain text link isn't actively clicked. This suggests an underlying positive effect, possibly related to overall email quality or perception by email clients.
- Accessibility and compatibility: Providing a plain text version ensures your email is readable across all devices and email clients, especially those that block images or render HTML poorly. This improves the user experience for a wider audience.
- Load speed: Plain text emails load faster due to their minimal file size, which is beneficial for recipients with slow internet connections or older devices. This can contribute to better engagement and less frustration for the user, improving overall email deliverability.
- Spam filter scrutiny: Email service providers (ESPs) and spam filters often analyze both the HTML and plain text parts of an email. A mismatch or poorly constructed plain text version could potentially raise red flags, while a well-aligned plain text version reassures filters of the email's legitimacy. A detailed explanation of this can be found on Smart Messenger's blog.
Key considerations
- Semantic consistency: Ensure that the content and (especially) the URLs in the plain text part are semantically consistent with the HTML version. Discrepancies can be a red flag for spam filters or cause user confusion.
- HTML rendering issues: If a plain text version performs significantly better, investigate potential rendering problems with your HTML across different mailbox providers or email clients. While Litmus (or similar tools) can show rendering, real-world delivery can differ.
- ESP link rewriting: Be aware of how your ESP handles click tracking and link rewriting for both HTML and plain text parts. Inconsistent handling could impact tracking or deliverability.
- Audience segmentation: Analyze conversion data broken down by mailbox provider or email client to identify specific segments where plain text might be outperforming HTML. This can pinpoint underlying issues or opportunities.
What email marketers say
Email marketers often observe varied impacts of plain text emails on their campaigns. While the primary focus is usually on visually rich HTML emails, many find that the inclusion or exclusive use of plain text can lead to unexpected positive outcomes, particularly in terms of engagement and conversion rates. This often stems from the simplicity and perceived authenticity of plain text messages, which can bypass certain rendering issues or recipient preferences that hinder HTML email performance. There's a strong belief that plain text can make emails feel more personal and less like mass marketing, fostering a stronger connection with the recipient.
Key opinions
- Higher deliverability perception: Many marketers report that plain text emails seem to have consistently high deliverability rates, possibly because they contain less complex code that could trigger spam filters. This makes them less prone to being caught by blocklists (or blacklists) and more likely to land in the inbox.
- Conversion surprises: Counter-intuitively, some marketers find that plain text emails can outperform visually elaborate HTML versions in terms of conversion, even by significant margins (e.g., 9% lift in one reported A/B test). This suggests a subtle, non-direct impact that transcends visual appeal.
- Reduced spam flagging: Plain text messages remove many of the common elements that spam filters scrutinize, such as excessive images or complex styling, which inherently reduces the likelihood of being marked as spam. This can be more effective than trying to change email templates for deliverability.
- Personalized feel: Plain text emails often convey a more personal, one-to-one conversational tone, which can build trust and rapport with recipients. This can lead to increased engagement even if the visual experience is minimal.
- HTML rendering dependency: A potential reason for plain text outperforming HTML is underlying issues with how the HTML version renders in specific email clients or for particular mailbox providers. Mailmunch highlights this point.
Key considerations
- A/B testing methodology: When observing a lift, marketers should meticulously analyze the data, especially segmenting by recipient ISP, to identify if the difference is consistent across providers or isolated to certain ones. This helps in understanding the root cause rather than just the correlation.
- Content representation: If an ESP provides an automated plain text version, marketers should verify its accuracy. A custom, well-written plain text version that genuinely reflects the HTML content is crucial for both deliverability and user experience.
- Link consistency: Ensure that tracking links, such as those with UTM parameters, are handled uniformly in both HTML and plain text versions. Inconsistencies could impact data accuracy or raise red flags with filters. It's important to understand how different elements of email content are weighted.
- HTML quality: If plain text is performing unusually well, it might indicate that the HTML itself has coding issues, is overly image-heavy, or contains patterns that frequently trigger spam filters (e.g., if a widely used template is associated with spam campaigns).
Marketer view
Marketer from Email Geeks shared A/B testing data showing a significant lift in conversion for emails that included a custom plain text version. This occurred despite no reported clicks on the dedicated plain text link, suggesting a subtle, indirect influence on recipient behavior or email processing.
Marketer view
Marketer from Email Geeks suggests that the direct deliverability impact of plain text versions might not be significantly noticeable. While it's a best practice, the observable difference in inbox placement might be subtle rather than dramatic.
What the experts say
Experts in email deliverability emphasize that while plain text emails can offer benefits, their direct impact on deliverability is often nuanced. They typically highlight the indirect advantages, such as reducing complexity that might otherwise trigger spam filters or addressing specific recipient preferences. The consensus leans towards a marginal direct effect on deliverability unless the HTML version has specific issues. However, the presence of a well-crafted plain text alternative contributes to a more robust email sending strategy by ensuring fallback options and wider compatibility. Technical aspects, such as how links are handled and rendered, are key areas of expert focus when evaluating plain text impact.
Key opinions
- Marginal direct impact: Experts generally believe that the direct deliverability improvement from including a plain text version is not substantial enough to be overtly noticeable, perhaps only a percent or two. The primary benefits are often indirect.
- Reduced filter triggers: Plain text messages inherently strip away many elements (like complex HTML tags or embedded images) that spam filters might find problematic, thereby reducing the chances of being blocked or blacklisted. This aligns with overall best practices for technical email deliverability.
- URL consistency is critical: A key concern for experts is the consistency of URLs between the plain text and HTML parts, especially if an ESP modifies them for click tracking. Discrepancies can negatively impact deliverability or user trust.
- Engagement feedback loop: While not a direct filter signal, improved user engagement stemming from a better plain text experience (for those who view it) can contribute positively to sender reputation over time, affecting future deliverability.
- HTML issues masked: If a plain text version significantly outperforms HTML, experts suggest it might indicate deeper HTML rendering problems with specific mailbox providers, rather than a direct plain text advantage. This implies a need to diagnose why emails are failing.
Key considerations
- Data analysis: When seeing A/B test results favoring plain text, experts recommend digging deeper into the data, specifically checking for consistency across different recipient ISPs. This helps isolate whether the cause is universal or provider-specific.
- UTM parameter impact: While UTM parameters are generally not part of spam filtering, experts acknowledge that if they were consistently found only in spam and never in legitimate mail, they theoretically could be. However, this is considered highly unlikely for standard UTM usage.
- HTML source code: The origin and quality of the HTML code itself can impact deliverability. If HTML is derived from generic templates or copied code that has been associated with spam, filters might flag it based on patterns. Ensure your HTML is clean and custom where possible. SpamResource frequently discusses evolving filter intelligence.
- Domain branding for links: Ensure that tracking links in both HTML and plain text versions are branded with your own domain, rather than a shared ESP domain. This contributes to a consistent and trustworthy sending identity, which mailbox providers favor.
Expert view
Expert from Email Geeks (Steve Atkins) posits that a significant deliverability difference from plain text alone is unlikely to be noticeably large. He suggests that if any difference exists, it would likely be a minor percentage (e.g., one or two percent), and further investigation into data consistency across recipient ISPs is warranted.
Expert view
Expert from Email Geeks (Steve Atkins) clarifies that the only true formatting available in the plain text part of an email is limited to basic elements like tabs and line breaks. This minimal formatting ensures maximum compatibility across all email clients and readers, adhering to the core nature of plain text.
What the documentation says
Official email standards and documentation consistently recommend including a plain text alternative alongside the HTML version in multipart/alternative emails. This practice is foundational for ensuring compatibility, accessibility, and robust deliverability across the diverse email ecosystem. The underlying principle is that email clients should have a fallback option, preventing messages from appearing broken or unreadable. Furthermore, documentation highlights that certain technical aspects of email processing, including spam filtering, can be influenced by the presence and quality of the plain text part. Adhering to these documented best practices is crucial for maintaining sender reputation and achieving optimal inbox placement.
Key findings
- Standard practice: Most email marketing best practices and technical specifications (like MIME multipart/alternative) recommend including both an HTML and a plain text version. This ensures that the message can be viewed by all recipients, regardless of their email client's capabilities.
- Spam filter analysis: Documentation indicates that spam filters often analyze the plain text version as part of their comprehensive spam scoring. A clean, accurate plain text version can positively influence the spam score, while a missing or mismatched version can raise red flags. This relates to how email blacklists (or blocklists) function.
- Enhanced accessibility: Including a plain text version improves accessibility for users with visual impairments who rely on screen readers, as well as those using text-only email clients or mobile devices with limited data. This broader reach contributes to higher engagement potential.
- Robust fallback: The plain text part serves as a robust fallback in scenarios where HTML fails to render, images are blocked by default, or the recipient's email client simply prioritizes plain text viewing. This ensures the core message is always conveyed.
- Perceived trustworthiness: Documentation suggests that providing a complete and well-formatted plain text version signals professionalism and adherence to email standards, which can subtly contribute to a sender's overall reputation and trustworthiness with mailbox providers. This influences how spam filters operate.
Key considerations
- Content parity: Documentation emphasizes that the plain text version should accurately reflect the content and intent of the HTML email. Any significant deviation can be seen as deceptive by spam filters, negatively impacting deliverability.
- Link fidelity: All clickable links in the HTML version should be present and functional in the plain text version. This means full, readable URLs, rather than hidden or malformed ones. This is crucial for both user experience and automated filter checks.
- Auto-generation vs. manual: While many ESPs auto-generate plain text from HTML, documentation often advises manually reviewing and refining it. Auto-generated versions can sometimes be messy or lack proper formatting, potentially hurting the message's effectiveness and its perception by filters. Email on Acid provides insights on this.
- Multipart/alternative MIME type: Correctly setting the Content-Type header to multipart/alternative is a fundamental technical requirement. This tells email clients that multiple versions of the message exist and they should display the most suitable one.
Technical article
Documentation from Smart Messenger states that by including a plain text version, senders significantly reduce the risk of being marked as spam. This practice improves overall deliverability rates, enhances accessibility for diverse users, and ensures broader compatibility across various email clients and devices, leading to a more reliable email experience.
Technical article
Documentation from Email on Acid explains that plain text emails offer fast loading and delivery. With no images or complex code, they load quickly for recipients and are less likely to encounter rendering issues that can delay or prevent display, thus contributing to a smoother user experience and reliable delivery.
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