How do ISPs measure email engagement?

ISPs measure engagement through various signals, including open rates, click-through rates, replies, forwards, and whether emails are moved to folders. For webmail clients, the duration an email is viewed (read length) may also be a factor, inferred from the activity of the tracking pixel .

Is email length more important than scroll depth?

Email length isn't inherently good or bad; its impact depends on content quality. A long email with valuable, engaging content can lead to a higher read length, which is a positive signal. However, a long, irrelevant, or poorly formatted email can deter engagement. Scroll depth is harder to measure consistently across all email clients compared to overall read length.

Can I track scroll depth in my email campaigns?

Directly tracking scroll depth in email campaigns is generally not possible for most email clients due to security restrictions on JavaScript . Most tracking relies on tracking pixels that confirm opens and sometimes time spent, but not how far down a user scrolled.

What content factors truly impact deliverability?

Content quality, relevance, mobile-friendliness, and clear calls to action significantly impact deliverability. Engaging content that encourages clicks, replies, and longer view times signals to ISPs that your emails are valuable. Conversely, content that leads to quick deletions or spam reports hurts your sender reputation. For instance, a high image to text ratio can also affect deliverability.

How do mobile users affect email length considerations?

Mobile users often scroll more, but they also have less patience for poorly formatted content. Long emails should be broken into digestible chunks with clear headings and responsive design. If content is clipped or difficult to read on mobile, users are likely to abandon the email quickly, which can negatively impact overall engagement metrics.

Does scroll depth or read length affect email deliverability? - Sender reputation - Email deliverability - Knowledge base

When we think about email deliverability, we often focus on technical aspects like DMARC, SPF, and DKIM, or sender reputation metrics such as open and click-through rates. However, a question I frequently encounter is whether less direct engagement indicators, like scroll depth or the actual read length of an email, play a role. It's an intuitive thought, especially with the rise of engaging, longer-form email content.

The idea is that if a recipient spends more time with your email, scrolling through its entirety or engaging with a significant portion of its content, this signals strong interest to Internet Service Providers (ISPs). But does this theoretical benefit translate into tangible improvements in your inbox placement? This article will explore the nuances of these metrics and their actual impact on how your emails land.

Understanding engagement metrics in email

ISPs and mailbox providers like Gmail,

Yahoo, and

Outlook constantly evaluate sender reputation to protect users from unwanted mail. They rely on a complex array of signals to determine whether an email is legitimate and desired by the recipient. These signals go far beyond simple opens and clicks.

Key engagement metrics include direct interactions such as replies, forwards, and emails moved to folders, as well as indirect ones like the time a user spends viewing an email. A high rate of positive engagement signals that your content is valuable to recipients, improving your sender reputation. Conversely, actions like deleting an email without opening it, or marking it as spam, negatively affect your reputation and can lead to future emails being sent to the spam folder.

While email marketing platforms track many metrics, specific data points like scroll depth are harder to reliably measure within the email environment itself. Unlike website analytics, where scroll depth tracking is common, the fragmented nature of email clients makes it a significant challenge to implement consistently.

Scroll depth and read length: do they matter?

The short answer is, it's complicated. For most desktop and mobile email clients, tracking precise scroll depth is not feasible due to technical limitations. These clients often render emails in ways that don't allow for the same granular tracking as a web browser. So, if you're sending emails to a diverse audience using various email clients, scroll depth is unlikely to be a direct factor in deliverability.

However, the situation changes when it comes to webmail interfaces. Since webmail clients are essentially web pages, ISPs can potentially track user behavior in a similar way to websites. Yahoo's sender performance feeds, for instance, explicitly mention "read length" as an indicator. This suggests that for webmail, the duration or extent to which an email is viewed could contribute to their internal assessment of engagement, and by extension, your sender reputation. While not a universally tracked metric across all email platforms, it's certainly on the radar of some major players.

It's important to distinguish between explicit tracking of scroll depth and the broader concept of read length. Read length often refers to the duration an email is open and active on screen, rather than how far down a user scrolled. This is a more easily measurable metric for ISPs, as it relies on the tracking pixel that loads when the email is opened. The longer the pixel is loaded and visible, the more likely the email is being read or actively engaged with.

Technical limitations and tracking nuances

The primary challenge with tracking scroll depth in emails lies in the inconsistent rendering environments. Unlike web pages, where JavaScript can precisely measure user interactions, most email clients block JavaScript for security reasons. This means traditional scroll tracking methods simply don't work in email.

Instead, email engagement is largely inferred from proxy metrics. The most common is the tracking pixel, a tiny image loaded when an email is opened. While this can tell you if an email was opened and for how long, it doesn't provide granular data on how much of the content was viewed. Some ISPs might use more sophisticated internal methods, especially within their own webmail interfaces, but these are proprietary and not directly accessible to marketers.

Another factor is email content length and its potential for clipping. If an email is too large, some email clients, especially Gmail, will clip the message, hiding the rest behind a view entire message link. This can negatively impact perceived engagement and potentially affect deliverability, even if the content is valuable. Clipped emails force an extra click, which can reduce overall interaction. This clipping impact on deliverability is something you should definitely consider.

Email client rendering

Variety: Emails display differently across desktop apps, mobile apps, and webmail interfaces. This inconsistency makes universal tracking of scroll depth impossible.
JavaScript limitations: Most email clients block JavaScript, which is essential for detailed interaction tracking on websites.

The role of content quality and user experience

While directly tracking scroll depth might be challenging, the underlying goal of creating content that holds a recipient's attention remains critical. ISPs prioritize delivering emails that users want to receive and engage with. Therefore, focusing on content quality and user experience is paramount. This includes factors like email design, mobile responsiveness, and the relevance of your message.

Email length, or read length, often correlates with the value a recipient perceives in your content. A long email isn't inherently bad if it's packed with engaging, relevant information that encourages sustained reading. However, if a long email is poorly organized, visually unappealing, or irrelevant, it's more likely to be abandoned quickly, signaling low engagement to ISPs. The Mailkarma AI blog emphasizes that email size and format directly affect deliverability.

A good user experience in email means ensuring your emails are easy to read on any device, load quickly, and provide clear value. This includes optimizing your image to text ratio and making sure your links are easily clickable. If your email is difficult to navigate or requires excessive effort to consume, users will likely disengage, which ISPs will notice.

The Nielsen Norman Group's research on scrolling and attention also highlights that while people scroll more, attention still concentrates above the fold. This principle applies to emails too, meaning your most crucial content should be immediately visible without requiring a deep scroll.

Optimizing for sustained attention

While direct scroll depth tracking in emails is limited, you can still optimize your content to encourage longer read times and overall positive engagement. These efforts indirectly signal to ISPs that your emails are valuable and worth delivering to the inbox. Here are some key strategies:

Prioritize initial content: Ensure your most important message or call to action is visible in the preview pane and without scrolling. This captures attention immediately.
Break up text: Use short paragraphs, bullet points, and clear headings to make content scannable. This improves readability and encourages readers to consume more of your message.
Mobile optimization: Design emails that render perfectly on mobile devices. Long, unformatted emails are a nightmare on small screens and will lead to quick abandonment.
Concise subject lines: A clear and compelling subject line encourages initial opens and sets expectations for content length.
Segment your audience: Send targeted content that resonates with specific segments. Highly relevant content increases the likelihood of full consumption and positive interaction.

The cumulative effect of these engagement signals contributes to your sender reputation. A high read length or deeper engagement, even if not directly tracked as scroll depth, will be reflected in positive ISP feedback and better deliverability. Conversely, a lack of engagement, or delayed email opening, can be interpreted negatively.

Good engagement indicator	Bad engagement indicator
Opening emails consistently	Emails deleted without opening
Clicking links within emails	Marking emails as spam/junk
Replying to emails	High bounce rates
Forwarding emails	Low click-through rates
Moving emails to folders	Numerous unsubscribes

Views from the trenches

Best practices

Craft compelling content that keeps recipients engaged from start to finish to encourage longer read times.

Ensure emails are responsive and load quickly across all devices to facilitate a smooth reading experience.

Use clear, concise subject lines and preheaders to set accurate expectations for email content.

Common pitfalls

Relying on email length alone as a positive deliverability signal without considering content quality.

Failing to optimize emails for mobile, leading to poor readability and quick abandonment.

Ignoring clipping issues in webmail clients, which can hide valuable content and reduce engagement.

Expert tips

Focus on the overall user experience within the email. If the content is valuable and easy to consume, recipients will naturally spend more time with it.

While direct scroll depth is hard to track, time spent on email is a general engagement signal that ISPs likely monitor, especially for webmail clients.

Consider that encouraging deep scrolling might be a marketing tactic for curiosity, not necessarily a direct deliverability strategy.

Expert view

Expert from Email Geeks says that for email clients, scroll depth is not a positive indicator for deliverability, but for webmail, it might be. The duration an email is open and looked at is probably measured.

2023-08-16 - Email Geeks

Marketer view

Marketer from Email Geeks says that there are rumors that Google measures the length of time spent with an email open.

2023-08-16 - Email Geeks

The path to better inbox placement

While the direct impact of scroll depth on email deliverability remains largely unconfirmed for most email clients, the concept of read length or time spent with an email is a more plausible indirect factor, particularly for webmail providers. The key takeaway is that ISPs value sustained, positive engagement.

Instead of chasing elusive metrics like pixel-perfect scroll depth, focus your efforts on creating high-quality, relevant, and mobile-friendly email content. When your subscribers find your emails valuable and easy to read, they will naturally spend more time engaging with them. This genuine engagement, whether measured by clicks, replies, or time spent, is what truly signals to ISPs that your messages belong in the inbox, not the spam folder or a blocklist.