How Gmail tab sorting can affect the visibility of marketing emails 

Gmail tab sorting is an inbox organization feature that automatically categorizes incoming emails into different tabs based on their content and sender type. As the Google Workspace article ‘Making Gmail’s tabbed inbox work better for you’ explains, “In 2013 we introduced tabbed inboxes in Gmail, which sorts your email into helpful categories in a simple, organized way. Over the years, we’ve heard from many Gmail users that these categories help keep their inboxes free of clutter so they can focus on getting things done.”

Gmail’s system uses machine learning and “a variety of signals”, including the sender, the type of content, and how users interact with similar emails, to decide placement. “Promotions [include] deals, offers, newsletters and other ‘call to action’ emails,” which means healthcare reminders, wellness campaigns, or service updates are often grouped alongside retail promotions. This placement influences how often recipients see and engage with healthcare marketing content. 

The Promotions tab is typically viewed less frequently than the Primary tab, which means marketing emails, including those from healthcare providers or health-related services, may receive fewer opens and clicks simply because users do not check the Promotions tab as regularly.

How Gmail’s tab sorting system works 

Gmail’s tab sorting system is a built-in feature that organizes incoming emails into different tabs such as Primary, Social, Promotions, Updates, and Forums. The feature uses Google's internal algorithms and user behavior signals like email frequency, engagement (opens, clicks), and sender reputation to classify emails and place them in the most appropriate tab. Users can customize which tabs are visible in their inbox and can drag emails between tabs to train Gmail on where they prefer certain messages to appear.

In collaboration with three companies, one study ‘Personalization in Email Marketing: The Role of Non-Informative Advertising Content’ “conducted randomized field experiments in which experimentally tailored email ads were sent to millions of individuals” and found that “adding the name of the message recipient to the email’s subject-line increased the probability of the recipient opening it by 20% … translated to an increase in sales leads by 31% … and a reduction in the number of individuals unsubscribing … by 17%.” Even when “such content is not likely to be informative about the advertised product or the company” can directly boost engagement.

The users quickly focus on the most relevant messages in the Primary tab while other types of communications are neatly segregated. Marketing emails and newsletters, for example, mostly end up automatically sorted into the Promotions tab, which acts as a separate holding space for commercial content. Similarly, social media notifications go to the Social tab, and system or service-related alerts are grouped under Updates.

How they impact email visibility 

When Gmail introduced its tabbed inbox interface in 2013, many marketers feared that emails landing in the Promotions tab would be treated like spam and ignored by recipients, thus killing email marketing effectiveness. While emails in the Primary tab tend to receive higher immediate open rates, emails routed to the Promotions tab are still actively checked by users, especially in contexts where consumers expect and look for deals, newsletters, and marketing content.

A similar dynamic has been observed in a Journal of Medical Internet Research study, where “many concerns have been raised about pharmaceutical companies marketing their drugs directly to consumers on social media.” The authors note that this form of electronic direct-to-consumer advertising (eDTCA) “can be interactive and, because it is largely unmonitored, the benefits of pharmaceutical treatment could easily be overemphasized compared to the risks.” In other words, like Promotions in Gmail, eDTCA shows how users still seek out and engage with marketing content when they expect it. 

Unlike the feared negative impact, this categorization actually helps prevent promotional emails from being misclassified as spam and lost altogether. The Promotions tab functions as a curated environment separating promotional emails from personal and social emails, creating a cleaner and more organized inbox experience for users. 

The organization helps emails get delivered to the inbox rather than the spam folder. Indeed, deliverability to any inbox tab (Primary, Promotions, or Social) is generally preferable to being diverted to spam or junk folders, where user engagement almost disappears.

What flags an email as a promotion 

Emails flagged as promotions typically exhibit distinct characteristics and metadata patterns that classification algorithms exploit to achieve effective sorting. One principal aspect concerns the content and structure of the email. Promotional emails commonly include marketing-related keywords and phrases, discount or offer language, pricing information, urgent calls to action, and brand names. These linguistic features can be quantitatively analyzed using NLP techniques to detect characteristic promotional text signatures.

In a Bulletin of the Transilvania University of Brasov article, “document retrieval is a form of text retrieval … and text retrieval is an important field of research nowadays because it is the foundation of all internet search engines.” Classification of promotional content is an application of these IR methods, where emails become “unstructured documents that correspond to the user’s information demands.”

Spam and promotional email classification employs term frequency-inverse document frequency (TF-IDF) metrics and word embeddings to gauge the presence and density of such marketing-related tokens in email bodies and subject lines. TF-IDF “intuitively assesses the significance of a specific term in a particular document,” giving weight to frequent promotional words while reducing the weight of generic terms. For example, frequent usage of terms like "sale," "offer," "buy now," "free," and monetary symbols serve as strong flags for classification models. 

The study went further by introducing term frequency–inverse sentence frequency (TF-ISF), which “operates at the sentence level rather than the document level … to enhance the retrieval of documents.” Another characteristic is the presence of multimedia and HTML formatting. Promotions often use rich HTML content with images, banners, and multiple links to enhance visual appeal and drive click-through rates.

Strategies to improve visibility

Using personalized language, contextually relevant subject lines, and avoiding all-caps or excessive punctuation reduces the likelihood of automatic categorization into promotional folders. Linguistic clarity and moderation of marketing jargon are critical because advanced classifiers deploy NLP models that weigh specific lexical features highly when deciding the category of emails.

A journal article published in The Scientific World Journal notes, “Spam filters using the structure and syntax of an email body in accordance with training techniques are common,” which means excessive reliance on predictable marketing terms or formats increases the risk of misclassification.

The structural format of the email itself is another element influencing classification. Emails laden with heavy HTML formatting, multiple images, flashy banners, or excessive hyperlinks tend to be flagged as promotional since its shown that these richer formats correlate with bulk advertising campaigns. 

To improve visibility, it is recommended to leverage simpler, mobile-friendly email designs with fewer embedded links and visuals, focusing instead on clear and concise messaging that resembles personal correspondence. The structural simplification helps circumvent automated detection systems that use heuristics such as link density and the presence of certain HTML tags to classify promotional content. 

See also: HIPAA Compliant Email: The Definitive Guide (2025 Update)

FAQs

Do healthcare marketing emails have to be HIPAA compliant?

Yes, healthcare marketing emails must comply with HIPAA when they contain protected health information (PHI) that identifies an individual.

What is considered marketing under HIPAA for healthcare emails?

Marketing under HIPAA is defined as any communication that encourages the recipient to purchase or use a product or service. Even newsletters or informational emails can fall under marketing if they promote healthcare services or products.

Is patient authorization always required for healthcare marketing emails?

Not always. HIPAA provides exceptions where authorization isn't required.