Can email sender reputation be harmed by third-party image or link hijacking?
Matthew Whittaker
Co-founder & CTO, Suped
Published 22 May 2025
Updated 14 Aug 2025
10 min read
Summary
The prospect of third-party image or link hijacking negatively impacting your sender reputation is a serious concern for email marketers. While theoretically possible and indeed observed in some niche scenarios, experts generally agree that this type of attack is less common and often less impactful than internal issues or broader malicious campaigns. Sender reputation, being a dynamic and continuously evaluated metric by mailbox providers, can recover from short-term anomalies.
Key findings
Real threat: Third-party hijacking of images or tracking links for malicious purposes is not just theoretical; it has been observed, particularly with the misuse of zero-length tracking links in spam to gain reputation benefits.
Short-term impact: While damaging, a hit to sender reputation from such hijacking is often a short-term issue that can be mitigated. Mailbox providers' algorithmic systems are designed to forget these transient issues over time, unlike persistent manual blocklists.
Detection sophistication: Mailbox providers use advanced algorithms to distinguish between legitimate and illegitimate uses of shared resources, by analyzing factors like the sending IP, sending domain, and the domains mentioned within the email content.
Shared resources risk: Senders using shared or free resources for content hosting (e.g., public image hosts, link shorteners) and ESPs with shared hosting domains are more susceptible to reputation impacts from the malicious activities of other users of those shared resources.
Internal factors dominate: Most email marketers cause more damage to their own reputations through poor practices or internal mistakes than any third-party malicious activity. Issues like problematic affiliate programs, unmanaged sub-departments, or incorrect list management often pose greater threats.
Key considerations
Proactive monitoring: While rare for direct attacks, continuous monitoring of your domain and IP reputation is crucial to quickly identify and address any unusual activity, whether internal or external.
Secure infrastructure: Protecting your email deliverability and sender reputation involves securing your entire email infrastructure. This includes using dedicated sending IPs and domains where appropriate, and ensuring proper authentication protocols like SPF, DKIM, and DMARC are in place.
Link and image domain management: Consider the impact of multiple or external domains in your emails, especially for image hosting. Opting for self-hosting images on your own domains can provide more control and reduce reliance on shared resources susceptible to abuse. You may also want to refer to this article from MarketingSherpa for some additional tips.
Affiliate program oversight: If you use affiliate programs, ensure rigorous oversight to prevent partners from engaging in spammy practices that could indirectly harm your reputation.
What email marketers say
Email marketers widely acknowledge the vulnerability of sender reputation to external factors, though many prioritize internal control and self-sabotage as more prevalent issues. While the threat of third-party hijacking is real, marketers often find that issues originating from within their own practices or extended networks (like affiliate programs) pose a more significant and frequent risk to their deliverability. The sentiment is that while external attacks are a concern, internal vigilance and adherence to best practices offer the most substantial protection.
Key opinions
Personal experience: Some marketers have directly observed instances where third-party hijacking of email elements (like images or tracking links) negatively impacted sender reputation.
High stakes: The potential for a malicious third party to destroy a marketer's sender reputation and career is a perceived, high-stakes risk, even if specific examples of blackmail are not readily available.
Threat landscape: Normal threats to reputation include dirty competitors, hackers, ransomware, and disenfranchised internal resources. Protecting against these requires a robust strategy.
Self-sabotage is bigger: Marketers frequently report that internal errors, such as sending to unmanaged lists or poor affiliate management, cause far more damage to their email deliverability than external malicious actors.
CEO-level risks: Anecdotes highlight issues like CEOs inadvertently marking company emails as spam or sending mass emails to every staff contact, demonstrating significant self-inflicted harm.
Key considerations
Focus on internal controls: Prioritize strengthening internal email sending practices, list hygiene, and team education. This will likely yield greater deliverability improvements than solely focusing on external threats.
Audit affiliate programs: Regularly audit and closely monitor any third-party affiliate programs or partnerships to ensure their email sending practices align with your brand's deliverability standards. This can prevent reputation issues in business partnerships.
Educate internal stakeholders: Educate all relevant internal stakeholders, including leadership, on email best practices and the impact of their actions on sender reputation. This proactive approach is essential for overall email deliverability, as discussed in HoneyBook's guide to email deliverability.
Monitor deliverability: Regularly check your deliverability rates and sender reputation metrics to quickly detect any anomalies, regardless of their origin. Understanding how email sending practices impact domain reputation is critical.
Marketer view
Email marketer from Email Geeks warns about the severe impact third-party actions can have on sender reputation, potentially jeopardizing careers. They emphasize that even when doing everything correctly, an external malicious actor could still significantly damage one's professional standing and deliverability.
12 Dec 2019 - Email Geeks
Marketer view
Email marketer from HoneyBook advises that a client or subscriber accidentally marking emails as spam can harm your reputation, especially if it leads to a sudden increase in complaints. They highlight the sensitivity of sender reputation to recipient feedback.
14 Mar 2024 - HoneyBook
What the experts say
Email deliverability experts agree that while third-party image or link hijacking can occur, its impact on a generally good sender's reputation is often manageable and less severe than other, more common issues. They highlight the evolution of spam filters towards algorithmic analysis of content and URLs, which allows for more nuanced detection and quicker recovery. A recurring theme is that issues stemming from within a company's own practices, or those of its partners, often pose a far greater risk than direct external attacks targeting images or links.
Key opinions
Real but not catastrophic: Experts confirm that third-party hijacking is a real issue, but generally categorize its impact on sender reputation as temporary and not catastrophic for otherwise good senders.
Focus on complex attacks: The more malicious forms of abuse often involve sophisticated tactics, such as spammers embedding legitimate tracking links as zero-length elements within their spam to unfairly benefit from the sender's reputation.
Algorithmic superiority: Modern algorithmic delivery systems are considered superior because they can forget past negative signals more quickly, allowing for reputation recovery. They analyze emails comprehensively, considering IP, domain, and content to differentiate legitimate from abusive patterns.
Internal risks outweigh external: Experts strongly emphasize that internal factors, such as poorly managed affiliate programs or rogue internal divisions, frequently cause more significant deliverability problems than direct third-party hijacking attempts.
Indirect funding of spam: Many large companies inadvertently fund spam by using affiliate structures that outsource work to partners who then engage spammers.
Key considerations
Understand filter evolution: Recognize that email filters have continuously evolved from simple IP-based reputation to more complex algorithmic analysis of content, URLs, and landing pages to combat evolving spam tactics. Keeping abreast of these changes, as detailed in an email deliverability best practices guide, is key.
Mitigate shared resource risks: If using shared, free resources for content hosting (e.g., image hosting, link shorteners), be aware that these can be impacted by other users' malicious activity. Consider how HTTP tracking links affect deliverability.
Prioritize internal hygiene: Devote significant effort to auditing internal email sending processes, affiliate programs, and ensuring consistent practices across all company divisions. This proactive approach helps prevent self-sabotage, which is a more prevalent cause of deliverability issues. This is also why understanding email authentication is essential.
Expert view
Expert from Email Geeks confirms that third-party hijacking of email elements is a real and not merely theoretical threat to sender reputation. This highlights the practical challenges email marketers face in maintaining control over their digital assets.
12 Dec 2019 - Email Geeks
Expert view
Expert from SpamResource states that third-party image hosting platforms can sometimes be abused, leading to deliverability issues if the platform itself becomes associated with spam. This necessitates careful consideration when choosing image hosting solutions.
15 Jan 2024 - SpamResource
What the documentation says
Official documentation and research often highlight the evolving nature of online abuse and the mechanisms used to combat it, which can indirectly relate to email sender reputation. Policies are put in place to address exploitation of legitimate site ranking signals or the spread of fraudulent communications. While not always directly addressing email, these documents underscore the broader principles of reputation management and the interconnectedness of online assets, including third-party content used in emails.
Key findings
Site reputation abuse: Documentation clarifies that using third-party content on a site (which could extend to email-linked content) to exploit its ranking signals is considered a policy violation. This principle extends to email, where the reputation of linked content reflects on the sender.
Phishing and fraud: Official guidance warns that fraudulent communications appearing from legitimate sources, often through email, can harm the reputation of the purported sender. This implies that even if your domain or image is hijacked, your reputation can suffer due to association.
Cyber threat environment: Cyber security overviews explain that malicious actors can masquerade as legitimate entities or hijack accounts to spread harmful content, which directly relates to the potential for image or link hijacking in emails.
Image security: While not malware, external images in emails loaded by insecure clients can pose risks. This highlights the importance of how email clients handle third-party content and how that can affect user perception and sender reputation.
Key considerations
Content reputation: Understand that the reputation of any third-party content (images, links, hosted files) included in your emails directly influences your overall sender reputation. This principle extends beyond just email to general web presence, as explained by Google for Developers.
Vigilance against phishing: Remain vigilant against phishing attempts that might utilize your brand's assets. Being reported for non-compliance or association with fraudulent activity can severely harm sender reputation, potentially leading to blocklisting or other deliverability issues, as described by Consumer Advice (FTC).
Hosting strategy: Carefully consider your image and link hosting strategy. While third-party services can be convenient, using your own domains for image hosting, for example, can give you more control over the associated reputation, as explored in the context of S3 buckets and custom domains for image hosting.
Blocklist understanding: Familiarize yourself with how email blocklists (or blacklists) work, as an association with malicious third-party activity could lead to your domain or IP being listed, impacting deliverability.
Technical article
Google for Developers states that exploiting a site's ranking signals by using third-party content is a violation of their site reputation abuse policy. This indicates that the reputation of linked or embedded content is intrinsically tied to the reputation of the hosting or sending entity.
06 Nov 2024 - Google for Developers
Technical article
The Canadian Centre for Cyber Security explains that cyber threat actors can masquerade as legitimate information providers or hijack social media accounts and websites. This directly applies to email, where a sender's legitimate assets (like images or links) could be similarly co-opted.
