Summary
Email deliverability is a shared responsibility between the Email Service Provider (ESP) and the business (sender) using the service, though the balance heavily favors the business. While ESPs provide the essential infrastructure and manage the sending environment, the ultimate success of an email reaching the inbox largely depends on the sender's practices, content quality, and recipient engagement. Businesses often mistakenly assume deliverability is solely the ESP's burden, leading to issues that could be prevented with proper internal strategies.
Key findings
- Sender's primary role: The vast majority of email deliverability responsibility, often cited as 80-90%, lies with the business or sender. This includes list hygiene, content quality, sending frequency, and recipient engagement.
- ESP's infrastructure contribution: ESPs are responsible for the foundational technical elements, such as ensuring proper email authentication (SPF, DKIM, DMARC) and managing network health to prevent broad blocklistings.
- Content and recipient management: The content of the message and the quality of the recipient list are critical factors influencing sender reputation, and these are entirely within the business's control. Bad practices in these areas can negate even the best ESP infrastructure.
- Shared IP implications: Even on a dedicated IP, the overall reputation of the ESP's network can impact deliverability if the ESP fails to adequately police spammers, as demonstrated by rare but impactful blocklistings of entire ESP networks by organizations like Spamhaus.
- Business autonomy: ESPs, even top-tier ones, will let me do any number of stupid things that will harm my deliverability. Businesses need to ensure they have robust email authentication in place.
Key considerations
- Proactive management: Businesses must proactively manage their email lists, maintain high engagement rates, and avoid sending unwanted messages to protect their sender reputation, which is a key factor influencing email deliverability.
- ESP due diligence: While the ESP's technical setup is usually robust, businesses should still select reputable ESPs that demonstrate strong anti-abuse policies and effective network management to ensure optimal transit of email to mailbox providers. MailerSend provides a helpful email deliverability guide for further insights.
- Authentication setup: Businesses are responsible for correctly configuring DNS records for email authentication protocols like SPF, DKIM, and DMARC, even if the ESP provides guidance or tools for this. Neglecting this can lead to emails going to spam.
- Understanding shared risks: Even with dedicated IPs, businesses can be indirectly affected by the broader reputation of their ESP's network if systemic issues lead to wider blocklistings. This risk emphasizes the shared nature of deliverability challenges.
What email marketers say
Email marketers widely agree that the bulk of email deliverability responsibility rests with the sender, typically assigning 80% to 90% to the business itself. They emphasize that while ESPs handle the technical infrastructure, a marketer's choices regarding list acquisition, email content, and sending practices are the primary drivers of inbox placement. Even a top-tier ESP cannot fully mitigate the impact of poor sender behavior. Marketers also note that differences in ESP quality, especially for mid-market providers, can introduce deliverability challenges not directly caused by the sender's actions, but ultimately, the customer is the one who can change providers.
Key opinions
- Sender-centric view: Many marketers state that 90% or more of deliverability responsibility lies with the company, focusing on list quality and content.
- ESP as infrastructure provider: ESPs are seen as providing the essential technical backend, which should be robust, but this alone doesn't guarantee inbox placement. The impact of ESPs on dedicated IPs is still present.
- Influence of content and list: The choice of what to send and to whom has a far greater impact on deliverability than the underlying email infrastructure.
- ESP quality variation: Some ESPs, particularly in the mid-market, may have suboptimal setups that can hinder deliverability, such as inadequate domain masking or issues with shared IPs. This highlights the importance of choosing an ESP with essential capabilities.
- Customer's ultimate control: Regardless of an ESP's shortcomings, the business (customer) is ultimately the only entity that can make the necessary changes, whether by improving practices or switching providers.
Key considerations
- Strategic importance: Marketers must prioritize developing a sound email strategy that focuses on audience engagement and valuable content to achieve optimal deliverability.
- Technical setup responsibility: While ESPs provide tools, marketers and their technical teams must ensure proper implementation of authentication protocols like SPF, DKIM, and DMARC. Salesforce provides insights into email deliverability best practices.
- Vendor assessment: Businesses should conduct thorough due diligence when selecting an ESP, looking beyond basic features to assess their deliverability support and network management.
- Proactive monitoring: Marketers should regularly monitor their deliverability metrics and be prepared to diagnose and fix issues, understanding that their actions are the primary influence.
Marketer view
Email marketer from Email Geeks believes it is a 50:50 game between senders and ESPs. Deliverability is subjective, but following the right blueprint helps minimize issues.
Marketer view
Email marketer from Email Geeks observes that a difference in deliverability between providers is possible. For instance, using an ESP on a shared IP that is heavily blocklisted can lead to legitimate emails being blocked or rejected due to poor IP reputation.
What the experts say
Experts in email deliverability consistently emphasize that while Email Service Providers (ESPs) handle crucial technical infrastructure, the overwhelming majority of deliverability responsibility, often quoted as 90% or more, rests with the business (sender). They highlight that factors such as content quality, list hygiene, and recipient engagement are paramount and are entirely within the sender's control. Experts also point out that even if an ESP's network experiences a rare, broad blocklist event, the underlying cause often traces back to issues that the ESP failed to sufficiently police among its users, underscoring the interconnectedness of deliverability factors. Ultimately, a good ESP can competently manage infrastructure, but it's the sender's practices that dictate long-term inbox placement.
Key opinions
- Overwhelming sender responsibility: The consensus among experts is that deliverability is largely on the company, with estimates ranging from 90% to 99.1% of the responsibility. This includes aspects like content and audience management.
- ESP's infrastructure role: ESPs are crucial for technical infrastructure, including email authentication (SPF, DKIM, DMARC) and ensuring timely email dispatch. They must also manage network cleanliness by preventing spammers. This is where reverse DNS resolution becomes important.
- Content and reputation: The content of emails and the quality of the recipient list are far more significant to sender reputation than infrastructure setup. These elements are directly controlled by the business.
- Shared IP risks and ESP policing: While rare, major blocklistings (like Spamhaus listing an entire ESP) indicate that the ESP has a responsibility to police its network and prevent widespread abuse, even if individual clients use dedicated IPs. This impacts IP reputation.
- No guarantee for bad practices: Even the most capable ESPs cannot guarantee deliverability if a sender engages in poor sending practices. They can advise against it, but the ultimate decision and consequences rest with the business.
Key considerations
- Comprehensive approach: Businesses must adopt a holistic approach to deliverability, understanding that both technical setup and engagement practices contribute significantly to inbox placement.
- Internal accountability: Companies should not solely rely on their ESP for deliverability, but instead foster internal expertise and processes to manage their sending reputation effectively.
- Proactive network management: ESPs have a continuous responsibility to monitor their network for abuse and take action to prevent widespread deliverability issues. This ongoing oversight is a key part of their value proposition, as highlighted by Word to the Wise's insights.
- Understanding ESP limitations: While ESPs handle delivery to the mail server, inbox placement (deliverability) is heavily influenced by sender reputation, which is primarily built and maintained by the business.
Expert view
Email expert from Email Geeks indicates that the ESP is highly responsible for ensuring infrastructure components like SPF and DKIM are correctly in place and that emails leave the system promptly. However, content has a much larger impact on reputation, making the content of a message and its recipient list the direct responsibility of the business.
Expert view
Email expert from Email Geeks suggests that nearly any ESP can competently manage the infrastructure aspects of email sending. The real challenge lies with the sender's practices, implying that once the technical foundation is set, the onus shifts almost entirely to the business for good deliverability.
What the documentation says
Official documentation and guides from various email platforms and industry resources highlight a clear division of labor in email deliverability. ESPs are typically responsible for maintaining robust sending infrastructure, including server uptime, IP reputation management on shared pools, and providing tools for authentication (SPF, DKIM, DMARC). However, these resources consistently emphasize that the business (sender) holds the primary responsibility for elements that directly influence recipient engagement and spam complaints, such as list quality, content relevance, sending frequency, and compliance with anti-spam laws. The documentation frames deliverability as an ongoing, collaborative effort where both parties have distinct but interdependent roles.
Key findings
- ESP's role in infrastructure: Documentation confirms ESPs manage the technical backend, including server architecture, IP warm-up processes, and fundamental email authentication mechanisms. They are responsible for the 'delivery' aspect.
- Sender's influence on inbox placement: Documentation consistently points to sender behavior as the most significant factor for 'deliverability,' meaning reaching the inbox. This encompasses list management, content, and recipient interaction.
- Shared responsibility model: Many guides articulate deliverability as a shared endeavor. While the ESP provides the vehicle, the sender is responsible for the 'driving' and ensuring the mail is wanted and legitimate. Understanding how email deliverability works is key.
- Importance of authentication: ESPs provide the framework for SPF, DKIM, and DMARC, but the sender is responsible for correctly implementing and maintaining these records within their DNS, crucial for establishing domain reputation.
- Engagement metrics: Mailbox providers heavily weigh engagement (opens, clicks, replies) and complaints when determining inbox placement. These metrics are directly influenced by the sender's campaign quality and audience targeting.
Key considerations
- Ongoing optimization: Documentation suggests that deliverability is not a one-time setup but an 'always-on process' requiring continuous monitoring and adaptation by the sender.
- Compliance with standards: Businesses must adhere to industry best practices and legal requirements (e.g., CAN-SPAM, GDPR) concerning list management and sending practices to avoid penalties and deliverability issues.
- Reputation building: Documentation emphasizes that a strong sender reputation is built over time through consistent positive engagement, which is primarily the sender's responsibility.
- Feedback loops: While ESPs manage feedback loops with ISPs, it's the sender's responsibility to act on the insights provided (e.g., remove complaining users) to improve deliverability.
Technical article
Documentation from MailerSend's blog explains that while ESPs handle backend processes, they have no control over certain factors that are the sender's responsibility. When emails don't get delivered, bad sender practices are often the cause, highlighting the need for senders to understand their role in the deliverability equation.
Technical article
Documentation from Klaviyo Help Center defines email deliverability as the placement of an email after it is successfully delivered to the recipient's mail server. This distinction is crucial: 'delivery' is the ESP's part, 'deliverability' is the sender's. The final inbox placement is heavily influenced by sender reputation, built through their sending habits.
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