Why has email deliverability dropped for affiliates?
Michael Ko
Co-founder & CEO, Suped
Published 13 Jul 2025
Updated 16 Aug 2025
9 min read
Many affiliate marketers have recently seen a noticeable decline in their email deliverability. This isn't an isolated incident. The email landscape is constantly evolving, with Internet Service Providers (ISPs) and mailbox providers continually refining their spam filters and sender requirements. For affiliates, who often operate in a sensitive space with higher scrutiny, these changes can have a disproportionate impact. I've been hearing a lot of discussions and observations that point to stricter filtering, particularly for mail that, while technically consented to, might not be what the recipient explicitly expected.
Understanding the unique challenges for affiliates
Affiliate marketing, by its nature, often involves sending emails to lists that may not have a direct, one-to-one relationship with the brand being promoted. This can lead to unique challenges that impact deliverability. Unlike direct brands building their own lists through explicit sign-ups for their content or products, affiliates frequently work with third-party lists or lead generation methods where the recipient's expectation of receiving specific promotional emails might be less clear.
One of the primary issues stems from how email addresses are acquired. If lists are purchased, rented, or gathered through less transparent means, they are inherently riskier. Such lists often contain a higher percentage of inactive users, spam traps, and recipients who haven't explicitly opted into receiving promotional content from your specific affiliate offer. This dramatically increases the likelihood of high bounce rates, spam complaints, and low engagement, all of which severely damage sender reputation.
Another significant hurdle is the lack of direct control over the sending infrastructure. Many affiliates rely on external email service providers (ESPs) or networks, where they might share IP addresses with other senders. If other users on these shared IPs engage in poor sending practices, it can negatively affect the reputation of all senders using that IP, including legitimate affiliates. This shared environment makes it harder to isolate and resolve specific deliverability issues.
Furthermore, the content itself can be a major factor. Affiliate emails often contain numerous links, promotional language, and sometimes generic messaging that can trigger spam filters. Balancing effective promotional messaging with content that aligns with deliverability best practices is a constant challenge for affiliates. Finding the right balance is key to ensuring your emails reach the inbox and engage your audience effectively, rather than getting caught by sophisticated filtering systems.
Key factors impacting affiliate deliverability
Several key factors contribute to a drop in email deliverability, especially for affiliates who face heightened scrutiny. These often revolve around sender reputation, list quality, and content relevance. Ignoring any of these areas can quickly lead to emails landing in the spam folder or being rejected outright, impacting campaign performance and return on investment.
Your sender reputation, both for your IP and domain, is paramount. Mailbox providers assign a reputation score based on various metrics, including spam complaint rates, bounce rates, engagement, and whether your IP or domain appears on any blocklists (or blacklists). A low sender reputation is a strong indicator to ISPs that your emails may be unsolicited or undesirable, leading them to filter your messages aggressively. This is why it’s critical to monitor your reputation consistently.
The quality of your email list is another critical determinant. Sending to outdated, unengaged, or purchased lists can significantly harm your deliverability. Purchased lists are especially problematic because they often contain spam traps, which are email addresses used by ISPs to identify senders of unsolicited mail. Hitting a spam trap can immediately land your domain or IP on a blocklist, severely impacting future deliverability. Ensuring that your subscribers genuinely opted in to receive your content is the cornerstone of good deliverability.
Finally, the content and sending patterns of your emails also play a vital role. Highly promotional content, excessive use of all caps, too many images without text, or frequent linking to external domains can trigger spam filters. Sudden spikes in sending volume or inconsistent sending patterns can also raise red flags with ISPs, leading them to suspect unusual or malicious activity, which can further degrade your sender reputation.
One of the most significant reasons for recent drops in deliverability, especially for affiliate marketers, has been the introduction of new, more sophisticated filtering mechanisms by major mailbox providers. Companies like Google and Yahoo (and Microsoft) have tightened their requirements for bulk senders, which directly impacts many affiliate email programs.
These new filters often target mail that, while potentially having technical consent, falls short on user expectation. For instance, if a user signs up for a newsletter from Company A, they expect emails from Company A. If that consent is then used to send promotional emails from Company B, C, or D (affiliates), even if legally permissible, it can lead to negative user signals like low engagement, ignored emails, or worse, spam complaints. ISPs are increasingly prioritizing the recipient's experience, and unexpected mail, regardless of technical compliance, is now a major red flag.
The latest updates from Google and Yahoo for bulk senders, which went into effect early this year, are a prime example. These requirements mandate strict email authentication (SPF, DKIM, DMARC), easy one-click unsubscribe options, and maintaining a very low spam complaint rate. Affiliates often struggle with the last point due to the nature of their list acquisition and content. If your spam rate crosses even a small threshold, such as 0.3%, your emails risk being sent directly to the spam folder or outright rejected.
This shift demands clear, in-your-face transparency about what recipients will receive and from whom. Anything less is likely to be flagged by these increasingly sophisticated filters. It's no longer enough to be technically compliant with anti-spam laws; you must also meet the implicit expectations of the email recipient.
New ISP requirements
Mailbox providers are tightening their rules. For affiliates, this means:
To counter these challenges and improve email deliverability, affiliates must adopt a more proactive and user-centric approach. Focusing on building a strong sender reputation and delivering value will be key to long-term success. These strategies can help minimize the risk of your emails being flagged as spam or blocked by stringent filters.
First, prioritize robust email authentication. Ensure your Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting & Conformance (DMARC) records are correctly set up and aligned. This proves to ISPs that you are who you say you are, which is fundamental for good deliverability. Without these, your emails are highly susceptible to being flagged.
Second, maintain impeccable list hygiene. Regularly clean your email lists to remove invalid or unengaged addresses. Implement a double opt-in process to ensure that every subscriber explicitly consents to receive your emails. This not only reduces bounces and spam complaints but also builds a more engaged audience. Consider a re-engagement campaign for inactive subscribers, and remove those who don't respond.
Finally, focus on providing genuine value in your content and encouraging engagement. Personalize your emails where possible, segment your audience to send more relevant messages, and avoid overly promotional language that might trigger spam filters. A clear, one-click unsubscribe option, as now required by major ISPs, is also crucial. Prioritizing the user experience will lead to higher open rates, click-through rates, and ultimately, better deliverability.
Old approach
List acquisition: Purchased or rented lists, or broad co-registration.
Content focus: Heavily promotional, generic copy with many links.
Authentication: Basic or inconsistent SPF/DKIM, no DMARC.
Unsubscribe: Hidden or multi-step unsubscribe process.
New approach
List acquisition: Double opt-in, clear consent for specific offers.
Content focus: Value-driven, personalized, clear calls to action.
Implement double opt-in for all new subscribers to confirm their explicit consent to receive emails.
Regularly clean your email lists by removing inactive subscribers, hard bounces, and known spam trap addresses.
Ensure your email authentication records, including SPF, DKIM, and DMARC, are correctly configured and monitored.
Segment your audience and personalize content to increase relevance and engagement, reducing spam complaints.
Common pitfalls
Using purchased or rented email lists, which often contain spam traps and unengaged contacts.
Sending emails with generic, overly promotional content and excessive use of spam trigger words or links.
Neglecting to monitor sender reputation, leading to unawareness of potential blocklist (or blacklist) issues.
Not providing a prominent and easy-to-use one-click unsubscribe option in your emails.
Expert tips
Focus on transparent consent: clearly communicate what emails subscribers will receive and from whom.
Prioritize user experience: unexpected emails, even if technically consented, can lead to negative signals.
Monitor your spam complaint rates closely; aim for well below the 0.3% threshold mandated by major ISPs.
Continuously analyze email performance data to identify specific providers experiencing deliverability drops.
Marketer view
Marketer from Email Geeks says that when deliverability drops, one should investigate which providers are affected, analyze bounce messages, and consider if the audience is B2B or B2C.
May 13, 2022 - Email Geeks
Marketer view
Marketer from Email Geeks suggests defining what constitutes a “drop in deliverability” and understanding the specific type of affiliate involved.
May 13, 2022 - Email Geeks
Navigating the affiliate email landscape
The recent drop in email deliverability for affiliates is a clear signal of an evolving email ecosystem. ISPs are increasingly prioritizing user experience and genuine engagement, making it harder for emails that don't meet these standards to reach the inbox. Success in affiliate email marketing now hinges on moving away from aggressive, broad-stroke sending tactics towards a more transparent, consent-driven, and reputation-focused approach.
By understanding the unique challenges of affiliate marketing, actively managing sender reputation, meticulously cleaning email lists, and optimizing content for relevance and engagement, affiliates can navigate this stricter landscape. Embracing these best practices will not only improve deliverability but also build more sustainable and profitable email programs in the long run. The goal is to ensure your messages are wanted and expected, leading to a healthier email relationship with your subscribers.
Google and 
Yahoo (and 
Microsoft) have tightened their requirements for bulk senders, which directly impacts many affiliate email programs.
