When is affiliate marketing email considered spam and how does it impact deliverability?
Michael Ko
Co-founder & CEO, Suped
Published 17 Jul 2025
Updated 14 Aug 2025
7 min read
Affiliate marketing email campaigns are a powerful way to drive sales and expand reach, but they walk a fine line between legitimate promotion and unwanted messages. The core challenge lies in how these emails are perceived by recipients and, more critically, by email service providers (ESPs) and internet service providers (ISPs).
It is not always easy to draw a clear distinction between a promotional email and what might be considered spam (or junk mail). My experience suggests that many affiliate mailings inherently feel a bit "spammy" because the sender isn't always the brand itself. This often leads to questions about how lenient or strict one should be when evaluating such campaigns.
Understanding when an affiliate marketing email crosses the line into spam is crucial for maintaining good deliverability and protecting your sender reputation. Poor practices can severely impact your ability to reach the inbox, affecting not just affiliate campaigns but all your email communications.
When is affiliate email considered spam?
When we talk about an email being considered spam, there's often a subjective element-what one person finds useful, another might see as junk. However, for ISPs and ESPs, "spam" is objectively defined by a set of criteria and user behavior. The most significant indicator is when recipients mark your email as spam or junk.
Major providers like Google and Yahoo have tightened their email sender guidelines, explicitly stating that a spam complaint rate exceeding 0.3% can lead to delivery issues. This low tolerance means that even a small percentage of negative feedback can have a significant impact.
Beyond complaints, other characteristics contribute to an email being flagged as spam. These include the lack of clear consent from the recipient, sending to old or unengaged email addresses (which might be spam traps), misleading subject lines, or content that appears overly promotional or deceptive. These factors signal to spam filters that the email may be unwanted.
The cornerstone of legitimate email
Proper consent is the bedrock of good email deliverability. Without it, your emails are unsolicited and prone to being marked as spam. For affiliates, ensuring that every recipient has explicitly opted in to receive marketing communications is not just a best practice, but a legal requirement under regulations like CAN-SPAM and GDPR.
Affiliate marketing practices and deliverability impact
Affiliate marketing, by its nature, can attract practices that negatively impact email deliverability. A primary concern is list acquisition. Many affiliates use questionable methods to build their email lists, such as purchasing lists or scraping addresses, which bypass explicit consent. Sending to these unverified or old lists significantly increases spam complaints and bounce rates, severely damaging sender reputation.
Another problematic practice is the use of generic or rapidly rotating domains and IP addresses. These setups often lack historical sending data, making them inherently suspicious to ISPs. When mail is sent through such channels, it frequently gets flagged as spam or blocked outright because it lacks the established trust associated with consistent, reputable sending.
The content and linking strategy also play a major role. Aggressive, hard-selling copy, excessive use of capitalized words, exclamation points, and a high density of links, especially to unfamiliar domains, can trigger spam filters. While affiliate marketing involves promoting products, the message should focus on relevance and value rather than just pushing a sale, which can be perceived as spammy. Specific spam words can also play a role, though their impact has evolved.
Legitimate affiliate marketing
Consent: Sending only to explicitly opted-in subscribers who expect your content.
Relevance: Providing valuable content and product recommendations that align with subscriber interests.
Transparency: Clearly identifying the sender and offering easy unsubscribe options.
Reputation: Building a positive sender reputation over time through consistent, desired sends.
Spammy affiliate marketing
List Acquisition: Using purchased, scraped, or unverified email lists.
Content: Aggressive, misleading, or overly promotional copy with excessive links.
Sender Identity: Using generic, rotating domains or masking the true sender.
Engagement: High spam complaint rates, low open rates, and frequent bounces.
The consequences of poor affiliate email deliverability
The most direct consequence of poor affiliate email practices is that your emails won't reach the inbox. They'll either be filtered into the spam folder, or worse, rejected outright. This leads to significantly lower open rates, click-through rates, and ultimately, lost revenue. For any marketer, this means wasted effort and a direct negative impact on campaign effectiveness. You can learn more about how to determine if marketing emails are going to spam.
Beyond individual campaign performance, sending spammy affiliate emails can lead to your domain or IP address being placed on an email blacklist (or blocklist). This is a severe consequence, as it means virtually all emails sent from that address or domain will be blocked by most major email providers. Recovering from a blocklist can be a lengthy and challenging process, requiring significant effort to rebuild trust with ISPs.
Perhaps the most damaging long-term effect is the harm to your overall brand reputation. If your affiliate partners engage in practices that lead to high spam complaints or blacklisting, the negative association can extend to your brand. I've seen situations where legitimate corporate emails from a brand were blocked simply because their affiliates were sending massive volumes of unsolicited mail with the brand's URL.
Example: Checking an IP address against a common DNSBLbash
dig +short -t A [IP_ADDRESS_TO_CHECK].zen.spamhaus.org
; Check if IP is listed on Spamhaus ZEN
dig +short -t A [IP_ADDRESS_TO_CHECK].sbl.spamhaus.org
; Check if IP is listed on Spamhaus SBL (Spamhaus Block List)
Strategies for maintaining strong deliverability
To navigate the complexities of affiliate marketing email without triggering spam filters, adherence to best practices is paramount. The first step is rigorous list management. This means acquiring subscribers through transparent, opt-in methods, ideally double opt-in, where users confirm their subscription. Regularly cleaning your lists to remove inactive or unengaged subscribers also helps maintain a healthy sender reputation.
Implementing robust email authentication protocols is non-negotiable. This includes Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting & Conformance (DMARC). These protocols verify that your emails are legitimate and prevent bad actors from spoofing your domain. Proper configuration of these records is a strong signal to ISPs that you are a trustworthy sender. Learn more in this guide to DMARC, SPF, and DKIM.
Finally, monitor your email performance diligently. Utilize tools like Google Postmaster Tools to keep an eye on your spam complaint rates, IP and domain reputation, and delivery errors. This data provides valuable insights into how your emails are being received and allows you to adjust your strategy proactively to prevent deliverability issues before they become severe.
Actively tracking deliverability metrics and feedback loops.
Ignoring spam complaints or bounce rates.
Views from the trenches
Best practices
Always prioritize explicit opt-in for all subscribers, ideally using a double opt-in process.
Maintain meticulous records of consent, including when and how each subscriber opted in.
Focus on delivering highly relevant content that matches subscriber expectations to minimize complaints.
Regularly clean your email lists to remove inactive users and protect against spam traps.
Ensure full compliance with email regulations like CAN-SPAM and GDPR, especially regarding unsubscribe options.
Common pitfalls
Relying on purchased or scraped email lists, which are often filled with unengaged or invalid addresses.
Ignoring high spam complaint rates or low engagement metrics, leading to reputation damage.
Using generic or frequently changing sending domains that lack a established reputation with ISPs.
Failing to clearly disclose that emails are from an affiliate or containing too many hard-sell promotions.
Not implementing or improperly configuring email authentication protocols like SPF, DKIM, and DMARC.
Expert tips
Monitor your engagement rates closely; low engagement can signal that your emails are not wanted.
Utilize feedback loops provided by major ISPs to promptly remove users who mark your emails as spam.
If using an Email Service Provider (ESP), leverage their reputation and tools to enhance your deliverability.
Segment your audience and tailor content to specific interests to improve relevance and reduce complaints.
Educate your affiliates on best practices and hold them accountable for their sending behavior.
Expert view
Expert from Email Geeks says if affiliate mail causes complaints or has other characteristics of spam, it can directly affect the delivery of your legitimate opt-in mail. In the case of affiliates, it often involves actual spammers who acquire addresses from questionable sources, with only a pretense of opt-in.
2018-05-15 - Email Geeks
Marketer view
Marketer from Email Geeks says affiliate marketing is a grey area, but I am comfortable receiving relevant links as long as they are not pushing a hard sell. It's about finding that balance between promotion and value.
2018-05-15 - Email Geeks
The path to better affiliate email deliverability
Navigating affiliate marketing in the email space requires a careful approach to avoid being labeled as spam. The definition of spam, while sometimes subjective, becomes very objective in the eyes of ISPs, driven largely by recipient complaints and engagement metrics. Ignoring these signals or adopting aggressive list acquisition and sending practices will inevitably lead to deliverability issues.
Prioritizing explicit consent, maintaining a clean email list, ensuring strong email authentication, and consistently monitoring your sending reputation are not just best practices-they are essential for the long-term success of your affiliate programs and the overall health of your email channel. By committing to ethical and transparent practices, you can ensure your affiliate marketing emails reach their intended audience, rather than the spam folder.
Google and 
Yahoo have tightened their email sender guidelines, explicitly stating that a spam complaint rate exceeding 0.3% can lead to delivery issues. This low tolerance means that even a small percentage of negative feedback can have a significant impact.
