What is the impact of adding promotional materials to transactional emails on foldering algorithms?
Matthew Whittaker
Co-founder & CTO, Suped
Published 20 May 2025
Updated 16 Aug 2025
8 min read
The question of whether to include promotional materials in transactional emails is one I encounter frequently. It's an appealing idea for marketers, offering an opportunity to engage customers further at a point when their attention is high, such as after a purchase or account update. However, it also raises significant concerns about how email providers, like Gmail and Outlook, will classify and folder these emails. The fear is that crucial transactional messages, like order confirmations or password resets, might end up in the promotions tab or, worse, the spam folder.
Transactional emails are fundamentally different from promotional emails. They are triggered by a user's action and convey essential, time-sensitive information. Think of shipping updates, password resets, or account notifications. Their primary purpose is to facilitate a transaction or provide critical service-related information. Promotional emails, on the other hand, aim to market products, announce sales, or drive conversions.
When you start blending these two categories, especially by adding promotional content, even a small block of recommended products, you introduce elements that foldering algorithms are designed to detect. These algorithms analyze various signals to determine an email's primary intent, influencing where it lands in a recipient's inbox. This article will explore the specific impacts this can have and how to navigate this complex area effectively.
Understanding email classification
Email service providers (ISPs) and mailbox providers use sophisticated machine learning algorithms to classify incoming emails. This classification goes beyond simply looking at the sending IP address or a declared 'transactional' label. These algorithms consider numerous factors to decide if an email is transactional, promotional, or even spam. The content of the email itself is a major signal.
Elements like images, GIFs, complex layouts, call-to-action buttons (especially those related to sales), discount codes, and marketing-oriented language all contribute to an email being identified as promotional. If these elements are present in an email, regardless of the sending IP, the algorithms are likely to classify it as marketing-related. This is why a transactional email might still end up in a promotional tab even if sent from a dedicated transactional IP.
User engagement also plays a critical role. ISPs track how recipients interact with your emails. If users frequently open, click, and reply to your transactional emails, but ignore or delete those that contain promotional content, the algorithms will learn from this behavior. This feedback loop helps ISPs refine their foldering decisions. A transactional email with promotional elements that consistently receives low engagement or, worse, spam complaints, is more likely to be classified as promotional or junk in the future.
It is not just about the technical sending configuration, but very much about the content and how recipients respond to it. This user feedback is incredibly powerful in shaping how ISPs classify your emails.
The risks of mixing content
The most immediate risk of adding promotional materials to transactional emails is that your critical transactional messages will start landing in the promotional tab. While the promotions tab is still part of the inbox, and some users actively check it, it is not the primary inbox that users typically monitor for essential communications. This can lead to delays in users receiving crucial information, such as shipping notifications or password resets, which can negatively impact their experience and potentially reduce trust in your brand.
A more severe consequence is the potential for increased spam complaints (This Is Spam - TIS). Even if recipients have opted into receiving promotional content, they might not expect it within a transactional email. If they perceive the email as primarily promotional rather than service-oriented, they might mark it as spam out of annoyance or confusion. A rise in spam complaints can significantly harm your sender reputation, leading to your emails being blocklisted or delivered to the junk folder for all recipients, including those who expect your transactional messages.
It is essential to understand that an ISP's filtering mechanism doesn't differentiate between opted-in or opted-out promotional content within a transactional email. The primary concern of the Gmail promotions tab (and similar tabs in other mailbox providers) is to organize the inbox for the user. If an email looks like marketing, it will be treated as marketing, regardless of intent or prior consent.
Legal implications
Beyond deliverability, there are also significant legal and compliance considerations. Regulations like GDPR, CAN-SPAM, and others have strict guidelines on what constitutes a transactional email versus a marketing email. Including promotional content can blur these lines and potentially lead to fines or legal issues, especially in regions with stringent privacy and email marketing laws. For example, a company was fined in the UK for sending service messages containing marketing content.
Despite the risks, the desire to cross-sell and upsell within transactional emails is understandable. These emails boast exceptionally high open rates because recipients are actively awaiting them. This presents a unique opportunity to capture attention and drive further business. The key lies in doing so tastefully and strategically, without compromising the email's primary purpose or your sender reputation.
One approach is to include only highly relevant, personalized promotional content. For example, in an order confirmation email, you might suggest complementary products or offer an upgrade related to their recent purchase. The promotional block should be small, clearly distinct from the main transactional content, and ideally placed at the bottom of the email.
Another consideration is ensuring that any promotional content is strictly limited to recipients who have explicitly opted in to receive marketing communications. This respects user preferences and minimizes the risk of unwanted content leading to spam complaints. However, even with consent, be mindful that a user expecting a shipping update might still be surprised or annoyed by a promotional banner, impacting their perception of your brand.
The dilemma
High visibility: Transactional emails have excellent open rates due to their anticipated nature.
Upselling opportunity: Leveraging existing engagement to drive additional sales or actions.
The risks
Folder misclassification: Essential emails potentially land in the promotional tab.
User dissatisfaction: Frustration if critical information is perceived as marketing.
To navigate the complexities of combining transactional and promotional content, implement a few key strategies. The goal is to maximize business opportunities while safeguarding your email deliverability and maintaining customer trust.
First, always prioritize the transactional nature of the email. The promotional content should be secondary, concise, and non-intrusive. It should never overshadow the primary message. A small, subtle banner or a few recommended products at the bottom of the email is often more effective and less risky than a prominent marketing block at the top.
Secondly, segment your audience carefully. Only include promotional content for users who have explicitly consented to receive marketing emails. This respects their preferences and reduces the likelihood of negative reactions. You might also consider A/B testing different approaches to see how your specific audience reacts to varying levels of promotional content within transactional emails. Monitor your deliverability metrics, such as open rates, click-through rates, and spam complaint rates, closely to understand the impact of your strategy.
Finally, be transparent. Clearly label any promotional sections and ensure that the primary transactional message is easily discernible. While a single sending IP can handle both, the content remains the most significant factor in how ISPs categorize emails. Maintaining a clear distinction in content and respecting user expectations will always be beneficial for your long-term email program health.
Best practice
Description
Content hierarchy
Ensure transactional content is dominant and placed at the top of the email. Promotional material should be secondary and appear towards the bottom.
Clear opt-in
Only include promotional content for users who have explicitly consented to receive marketing messages.
Relevance and personalization
Make promotional content highly relevant to the specific transaction or user behavior, enhancing its value.
Subdomain separation
Consider using separate subdomains for transactional and promotional emails to manage reputation independently, especially if promotional content is significant.
Monitor performance
Regularly track key metrics like open rates, click-through rates, and spam complaint rates to assess impact.
Views from the trenches
Best practices
Always keep the primary purpose of the email transactional; any promotional content should be supplementary and clearly separate.
Segment your audience carefully, only showing promotional content to those who have explicitly opted in for it.
Test different approaches and monitor your email deliverability metrics closely to understand the real-world impact.
Ensure legal compliance by checking regional regulations regarding mixed content in transactional emails.
Common pitfalls
Overwhelming the recipient with too much promotional content, which can lead to confusion and annoyance.
Assuming that because a user opted in for promotions, they want them in every type of email, especially transactional ones.
Not monitoring spam complaint rates or inbox placement carefully after implementing a hybrid email strategy.
Failing to separate sending IPs or subdomains for transactional and promotional mail, which can negatively impact reputation.
Expert tips
Focus on personalization and relevance for any promotional elements, making them genuinely valuable to the recipient.
Consider a very subtle, almost unnoticeable promotional footer or sidebar rather than a full block if you must include mixed content.
Educate your customers about the promotions tab if they complain about emails landing there, as it is still part of the inbox.
Prioritize user experience and trust above short-term revenue gains from mixed emails to maintain long-term deliverability.
Marketer view
Marketer from Email Geeks says that using the same IP for mixed transactional and promotional content does not inherently affect how consumer ISP filters classify the email.
2021-08-04 - Email Geeks
Marketer view
Marketer from Email Geeks says both the promotions tab and the primary tab are considered part of the inbox, and users typically check both, so excessive concern over placement might be unnecessary.
2021-08-04 - Email Geeks
Strategic approach to email content
Adding promotional materials to transactional emails presents both an opportunity and a risk. While it can offer an additional touchpoint for marketing, it also carries the potential to disrupt email deliverability and damage customer experience. ISPs use sophisticated algorithms that prioritize content and user engagement over declared email types or IP addresses when determining foldering.
A strategic approach involves careful consideration of content, user consent, and continuous monitoring of deliverability metrics. By prioritizing the transactional nature of the email, keeping promotional content subtle and relevant, and adhering to compliance regulations, businesses can explore hybrid email strategies without unduly risking their core communication channels. The ultimate goal is to maintain recipient trust and ensure that essential information always reaches its intended destination.
