Does not having a plain text email version affect deliverability?
Matthew Whittaker
Co-founder & CTO, Suped
Published 4 May 2025
Updated 19 Aug 2025
7 min read
I recently encountered a situation where an email service provider was unable to generate a plain text version of emails, and it raised concerns about how this might impact deliverability. It's a common question in the email marketing world, especially when inbox placement tests suggest that a plain text alternative is necessary.
The idea that a missing plain text version significantly harms deliverability is a common misconception, often rooted in older spam filtering methods. While a plain text part is technically recommended, the reality in modern email ecosystems is more nuanced.
Many contemporary email clients and spam filters have evolved to handle HTML emails robustly, and the absence of a separate plain text version isn't typically a primary factor in emails landing in the spam folder. However, this doesn't mean it's entirely irrelevant. Understanding the full picture helps in making informed decisions about your email strategy.
Historical context and current reality
Historically, spam filters like SpamAssassin would assign a higher spam score to emails that lacked a plain text version. This led to the widespread belief that including one was crucial for email deliverability. While these older systems still exist, their influence on overall inbox placement has diminished significantly.
Modern spam filters (or blocklists) now prioritize a broader range of signals. These include sender reputation, engagement metrics, authentication protocols (like SPF, DKIM, and DMARC), and content quality.
If you're using a reliable email service provider (ESP), they will almost certainly create a multipart/alternative email. This means the email contains both an HTML version and a plain text version within the same message. Email clients then choose which version to display based on the recipient's preferences or capabilities.
Understanding multipart/alternative
The multipart/alternative MIME type is standard for sending emails that include both HTML and plain text versions. It instructs the email client to display the 'best' version it can handle, usually the HTML version if supported. If not, it falls back to the plain text version. This is the ideal scenario for compatibility and deliverability.
Example of a multipart/alternative email headeremail
Content-Type: multipart/alternative; boundary="_----------=_1683832145325890"
--_----------=_1683832145325890
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
This is the plain text version of your email.
--_----------=_1683832145325890
Content-Type: text/html; charset="utf-8"
Content-Transfer-Encoding: quoted-printable
<html><body>
<p>This is the <b>HTML</b> version of your email.</p>
</body></html>
--_----------=_1683832145325890--
In cases where an ESP truly sends only an HTML version without any plain text part, the primary risk isn't necessarily deliverability to the inbox but rather the user experience for recipients with specific email clients or accessibility needs. For example, some older clients, or those with very strict security settings, might strip out HTML, leaving a blank or unreadable message. Furthermore, screen readers rely on the plain text version or proper HTML structure to convey content effectively.
It's also worth noting that if an HTML email is poorly coded, excessively large, or heavily reliant on images without alt text, it could indirectly affect deliverability because it signals low quality to filters. This isn't because of a missing plain text version, but because the HTML itself is problematic.
Ultimately, the consensus among deliverability professionals is that the absence of a distinct plain text version is a relatively minor factor compared to other critical elements. While it's always best practice to include both HTML and plain text for maximum compatibility and accessibility, its absence alone is unlikely to be the sole cause of widespread deliverability issues.
Other critical deliverability factors
When assessing email deliverability, it's crucial to look beyond just the plain text version. Many factors carry far more weight in determining whether your emails reach the inbox or get flagged as spam (or added to a blacklist).
One of the most important aspects is your sender reputation. This is built over time based on factors like consistent sending volume, low spam complaint rates, high engagement (opens and clicks), and low bounce rates. A strong sender reputation signals to internet service providers (ISPs) that you are a legitimate sender.
Email authentication protocols like SPF, DKIM, and DMARC are fundamental. These records verify that an email originated from an authorized sender and hasn't been tampered with. Their proper configuration is far more impactful on deliverability than the presence or absence of a plain text version.
HTML emails
Visual Appeal: Allows for rich formatting, branding, images, and interactive elements, enhancing the recipient's experience.
Tracking: Enables tracking of opens, clicks, and other engagement metrics crucial for campaign analysis.
Modern Expectation: Most users expect visually appealing and branded emails from businesses.
Plain text emails
Simplicity: Consists only of text, no images, styling, or complex code.
Compatibility: Displays correctly across all email clients, including older ones or those with restricted HTML viewing.
Accessibility: Easier for screen readers and other assistive technologies to interpret.
Interpreting deliverability test results
The main reason you might still be seeing warnings from GlockApps or similar tools about missing plain text versions is often related to their comprehensive testing methodologies, which account for a wide array of email client behaviors and older spam filters. While these warnings are valuable, they should be interpreted within the broader context of your overall email program.
Focusing solely on the plain text version can distract from more significant deliverability challenges. For instance, high bounce rates, low engagement, or recipient complaints are far more detrimental to your sender reputation than the technical absence of a plain text part within a multipart/alternative email. I've often seen deliverability issues traced back to poor list hygiene or content that triggers spam filters for other reasons.
A properly coded HTML email, even without an explicitly separate plain text version (though most ESPs add it automatically), will generally perform well if all other deliverability best practices are followed. This includes ensuring your image to text ratio is balanced and that your unsubscribe process is clear.
If your current ESP truly cannot produce any form of plain text part within a multipart message, even automatically generated, it might be a sign of an outdated platform. While it may not be the primary cause of poor deliverability, it limits compatibility for certain recipients and is generally not reflective of a robust email sending infrastructure. In such cases, considering a platform that adheres to modern email standards (such as HubSpot or GetResponse) might be beneficial for overall email program health. For example, Yotpo has recently exited the email business, indicating the need to re-evaluate your platform choice.
Prioritizing deliverability efforts
Focus on sender reputation
Prioritize maintaining a strong sender reputation through consistent sending, low bounce rates, and high engagement.
Implement authentication
Ensure your DMARC, SPF, and DKIM records are correctly configured and monitored. These are fundamental for email security and deliverability.
List hygiene
Regularly clean your email lists to remove invalid or unengaged addresses. This reduces bounce rates and spam trap hits (which can lead to blocklisting).
Content quality
Ensure your email content is relevant, engaging, and free of typical spam triggers. Avoid excessive use of images, particularly without alt text, and balance text with visuals.
While not having a plain text version for HTML emails isn't ideal, it's typically a minor concern compared to factors like sender reputation, email authentication, and list quality. Modern email systems and ISPs focus on these broader signals to determine deliverability. As such, any warnings from GlockApps should be considered as one data point among many, and not necessarily an indicator of significant deliverability impact.
I recommend you focus on the foundational elements of email deliverability first. These include proper sender authentication (SPF, DKIM, DMARC), maintaining a clean email list, and ensuring consistent, positive engagement from your recipients. These steps will have a much greater impact on your inbox placement than the absence of a plain text version alone.
Views from the trenches
Best practices
Always aim for multipart/alternative emails to ensure maximum compatibility and accessibility for all recipients, even if your ESP claims it's not strictly necessary for deliverability. This provides a fallback for clients that cannot render HTML.
Regularly monitor your email engagement rates, including opens, clicks, and especially spam complaints. High complaint rates are a far more significant indicator of deliverability issues than a missing plain text version.
Implement and monitor email authentication protocols (SPF, DKIM, DMARC) rigorously. These are critical for proving your legitimacy as a sender and preventing phishing and spoofing.
Common pitfalls
Over-relying on a single metric from an inbox placement test, such as a warning about plain text, without considering the full spectrum of deliverability factors. These tools provide valuable insights but need holistic interpretation.
Neglecting the sender reputation in favor of minor content optimizations. A strong reputation, built on consistent positive sending behavior, is the bedrock of good deliverability.
Sending image-only emails without proper alt text, which can lead to accessibility issues, poor user experience when images are blocked, and higher spam scores from some filters.
Expert tips
Use an email deliverability monitoring tool to track your inbox placement and reputation across various ISPs, not just relying on one-off tests for specific issues.
Segment your audience and personalize your content. Higher relevance leads to better engagement, which positively impacts your sender reputation.
Periodically review your email design and content to ensure it's responsive and loads quickly on all devices, providing a seamless experience for recipients.
Expert view
Expert from Email Geeks says: Historically, SpamAssassin used to score emails better if they included a text version, which is the origin of much outdated guidance. However, the chances of widespread deliverability issues due to the lack of a text version are minimal today.
2025-08-11 - Email Geeks
Expert view
Expert from Email Geeks says: I consider the absence of a plain text version to be a pretty low concern when it comes to deliverability. Factors such as email consent and proper opt-in practices will have a much greater impact.
2025-08-11 - Email Geeks
Final thoughts on plain text and deliverability
While a plain text email version is a good practice for compatibility and accessibility, its absence is rarely the sole cause of significant email deliverability problems in today's landscape. My experience indicates that modern spam filters and ISPs prioritize a sender's overall reputation, proper email authentication, and recipient engagement.
Therefore, if you're facing deliverability challenges, I recommend directing your efforts towards strengthening your sender reputation through consistent positive sending behavior, ensuring robust SPF, DKIM, and DMARC configurations, and maintaining a healthy, engaged email list. These foundational elements will yield far more impactful results for your inbox placement.
GlockApps or similar tools about missing plain text versions is often related to their comprehensive testing methodologies, which account for a wide array of email client behaviors and older spam filters. While these warnings are valuable, they should be interpreted within the broader context of your overall email program.
