Will iOS Outlook 'Read More' clipping impact email deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 14 Jul 2025
Updated 16 Aug 2025
9 min read
It can be unsettling to send an email campaign, only to discover that some recipients are seeing a "Read More" link instead of the full message. This is a common phenomenon known as email clipping, and while it's most frequently associated with Gmail, it also occurs in other email clients, including Outlook on iOS devices. The immediate concern for many senders is whether this clipping will negatively impact their email deliverability.
Understanding why your email might be clipped in Outlook iOS and what that means for your messages reaching the inbox is crucial. It often comes down to the technical limitations of the email client itself, rather than a signal of poor sender reputation or a blocklist (or blacklist) issue. Let's dive into the specifics of iOS Outlook clipping and its actual implications for your email deliverability.
Understanding email clipping on iOS Outlook
Email clipping occurs when an email's content exceeds a certain size or dimension limit set by the email client. When this limit is reached, the client truncates the message and displays a Read More or View entire message link to reveal the rest of the content. This is a design choice by the email client to improve loading times and user experience for lengthy messages, especially on mobile devices.
While Gmail is well-known for its clipping behavior, especially for emails exceeding 102KB in HTML size, Outlook on iOS also has its own specific clipping thresholds. Research and community discussions, like those found on GitHub email bugs, indicate that the Outlook app on iOS often clips emails longer than 5000 pixels in height. This is a significant difference from HTML file size, focusing purely on the rendered length of the email.
The critical point here is that if your email is clipped, it means it successfully landed in the recipient's inbox and was opened, at least partially. The clipping itself is a post-delivery rendering behavior, not a pre-delivery filtering action. It is not an indicator that your email was flagged as spam or that your sender reputation is suffering. The email has made it past the initial spam filters and authentication checks.
However, while clipping doesn't directly block your email, it can significantly affect the user experience and, consequently, your engagement metrics. If key information or calls to action are hidden behind a "Read More" link, recipients might not see them, leading to lower conversion rates.
Outlook iOS clipping: Understanding the limits
Outlook's iOS app generally clips emails that exceed approximately 5000 pixels in height. This limit is based on the rendered height of the email, including all HTML, CSS, and images. Unlike Gmail's HTML file size limit, Outlook iOS considers the visual length of your email content.
To avoid clipping, you should design your emails with a focus on conciseness and efficient use of space. This means optimizing image sizes, minimizing verbose content, and structuring your layout to keep essential information visible without requiring the recipient to click "Read More."
Clipping versus deliverability: A clear distinction
The good news is that seeing a "Read More" link in iOS Outlook is not a direct indication of a deliverability problem. When an email is clipped, it means the message has already passed through the various security and filtering layers of the recipient's mail server and landed in their inbox. If it were truly a deliverability issue, the email wouldn't have reached the inbox at all, potentially ending up in spam folders or being rejected outright.
Email deliverability is about your message successfully reaching the intended inbox, avoiding the spam folder or outright rejection. It's influenced by factors such as sender reputation, email authentication (like SPF, DKIM, and DMARC), content quality, and recipient engagement over time. Clipping, conversely, is a client-side rendering issue that happens after delivery.
Consider it this way: if a newspaper article is too long for a single page and continues on another, it doesn't mean the newspaper wasn't delivered to your home. It simply means you need to turn the page to read the rest. Similarly, Outlook iOS is merely managing the display of lengthy content for a better mobile viewing experience.
While clipping itself doesn't cause deliverability problems, prolonged low engagement resulting from clipped emails could, indirectly, impact your sender reputation. ISPs observe how recipients interact with your emails. If many users consistently fail to engage with your clipped messages, it could signal to the ISP that your content isn't relevant or engaging, potentially leading to future filtering issues.
Clipping (rendering)
Definition: Occurs when an email's content exceeds a client's size or dimension limit.
Cause: HTML size, image sizes, or overall rendered height (e.g., Outlook iOS 5000px). Email is already in the inbox.
Impact: Primarily affects user experience and engagement metrics (e.g., click-through rates) as content is hidden. Does not directly cause emails to go to spam.
Deliverability (inbox placement)
Definition: Whether an email successfully reaches the recipient's primary inbox.
Cause: Influenced by sender reputation, authentication, IP/domain history, content relevance, and list hygiene.
Impact: Determines if your email is seen at all. Poor deliverability leads to messages in spam or bounce backs, negating all marketing efforts.
Impact on engagement and long-term sender reputation
While email clipping itself does not directly affect whether your email lands in the inbox (i.e., its deliverability), it can significantly impact how recipients engage with your message. If a crucial call to action (CTA) or essential information is hidden behind a "Read More" link, the recipient might miss it, reducing your email's effectiveness and potentially leading to lower click-through rates. This isn't ideal for your campaign performance.
Engagement is a key factor in long-term deliverability. Internet Service Providers (ISPs), including Microsoft Outlook, monitor how recipients interact with your emails. If emails are consistently clipped and result in lower engagement (fewer clicks on the "Read More" link or no further action), this can indirectly signal to the ISP that your content isn't relevant or valuable to your subscribers. Over time, this could negatively influence your sender reputation, leading to future inbox placement issues.
Therefore, while clipping isn't a direct block, it represents a missed opportunity for engagement and can contribute to a decline in perceived content quality by ISPs. It's essential to design emails that convey their core message and primary call to action within the visible portion before any clipping occurs. This ensures your message has the best chance of resonating with your audience.
To mitigate the risk of engagement issues, focus on efficient email design. As Mailjet explains, when an email is clipped, it's an engagement issue, especially if the call to action is hidden. This underscores the need to be mindful of overall email length and HTML complexity.
Email client
Clipping threshold
Primary impact
Outlook (iOS)
Approx. 5000px rendered height
User experience, potential for missed CTAs
Gmail
102KB HTML file size
User experience, tracking pixel issues, potential for missed CTAs
Other clients (less common)
Varies by client and device, often related to HTML size or complex rendering
Minor user inconvenience
Strategies to prevent clipping and optimize email content
To prevent your emails from clipping in iOS Outlook, the primary strategy is to reduce the overall rendered height of your email. This involves optimizing your HTML structure, minimizing nested tables, and being judicious with spacing. Every element contributes to the overall height, so a streamlined design is key.
Image optimization also plays a crucial role. While images don't directly add to HTML file size in the same way as text, their dimensions contribute significantly to the rendered height of your email. Ensure your images are compressed and sized appropriately for web and mobile viewing. Using the correct image formats and dimensions can help reduce the overall visual length. Consider reviewing guidelines on how images affect deliverability.
Beyond technical adjustments, focus on content strategy. Prioritize your most important message and call to action "above the fold" (the visible area before clipping occurs). Ensure that recipients can grasp the main purpose of your email and take desired action without needing to click "Read More." If you have lengthy content, consider directing recipients to a landing page rather than embedding everything directly in the email. This can also improve tracking accuracy.
Finally, regular testing across various email clients and devices, including Outlook on iOS, is essential. This allows you to identify and address clipping issues proactively before they impact your audience. Utilizing Outlook’s sender requirements and understanding the implications of new updates like iOS 18 can help you prepare for changes in email rendering and user experience.
Example of HTML optimization for reduced email heightHTML
<style>
/* Optimize image rendering for responsive design */
img {
max-width: 100%;
height: auto;
display: block;
}
</style>
<body>
<table role="presentation" border="0" cellpadding="0" cellspacing="0" width="100%">
<tr>
<td>
<!-- Keep content concise and to the point -->
<p style="font-size:16px;line-height:24px;">Your primary message here. Ensure calls to action are visible without scrolling.</p>
</td>
</tr>
<tr>
<td>
<a href="#" target="_blank" style="display:inline-block;padding:12px 24px;background-color:#0078D4;color:#ffffff;text-decoration:none;border-radius:5px;">Click Here</a>
</td>
</tr>
</table>
</body>
Views from the trenches
Best practices
Keep email HTML code clean and efficient, removing unnecessary tags or excessive inline styles.
Design with a mobile-first approach, prioritizing essential content above the fold to ensure visibility.
Optimize all images for web, compressing them without significant loss of quality.
Common pitfalls
Over-reliance on complex HTML structures or deeply nested tables that inflate email height.
Using very large, unoptimized images that contribute significantly to the rendered pixel height.
Placing critical calls to action or key information towards the bottom of long emails.
Expert tips
For iOS Outlook, focus on rendered height optimization rather than just HTML file size.
A segmented content approach can work well, where a concise summary is in the email and full details are linked externally.
Regularly audit your email templates for hidden code bloat that might be contributing to clipping.
Marketer view
Marketer from Email Geeks says they see clipping on lengthy newsletters in Outlook iOS, but not usually on shorter marketing messages, suggesting that email length is the primary factor.
July 27, 2022 - Email Geeks
Expert view
Expert from Email Geeks says that if the mail is being displayed, it has been delivered to the inbox and opened by the user, which provides positive signals. It is unlikely that anything other than reporting it as spam will affect future delivery of similar emails.
July 28, 2022 - Email Geeks
Key takeaways and next steps
In conclusion, the presence of a "Read More" link (or email clipping) in iOS Outlook does not, by itself, negatively impact your email deliverability. This behavior indicates that your email has successfully reached the recipient's inbox and is a function of how the Outlook app manages the display of longer messages, particularly on mobile devices. The core issue is one of rendering and user experience, not a blocklist (or blacklist) designation or a failure in your sending infrastructure.
However, ignoring clipping can have an indirect effect on your email program's success. If recipients consistently miss your primary message or call to action due to clipping, it can lead to reduced engagement, which over time, might subtly influence how ISPs perceive your sender reputation. Therefore, while clipping isn't a deliverability blocker, optimizing your emails to avoid it in key clients like Outlook iOS is a best practice for maximizing engagement and maintaining a healthy sender reputation.
Microsoft Outlook, monitor how recipients interact with your emails. If emails are consistently clipped and result in lower engagement (fewer clicks on the "Read More" link or no further action), this can indirectly signal to the ISP that your content isn't relevant or valuable to your subscribers. Over time, this could negatively influence your sender reputation, leading to future inbox placement issues.
