What deliverability and compliance tools should a new ESP implement?
Michael Ko
Co-founder & CEO, Suped
Published 12 Jun 2025
Updated 19 Aug 2025
6 min read
Starting a new Email Service Provider (ESP) in today's landscape presents unique challenges, especially concerning email deliverability and compliance. The market is mature, and mailbox providers like Gmail and Yahoo are continuously introducing stricter requirements. For a nascent ESP, building a reputation and ensuring messages reach the inbox, rather than the spam folder, is paramount. This requires a robust set of tools and practices from day one to manage sender reputation, prevent abuse, and maintain a high level of compliance.
It’s not just about sending emails; it's about sending them responsibly and effectively. Implementing the right infrastructure, monitoring solutions, and compliance protocols is crucial for long-term success. These foundational elements help mitigate risks, build trust with internet service providers (ISPs), and ultimately ensure your clients' emails are delivered reliably.
Without these essential components, a new ESP risks frequent blocklistings (or blacklistings), poor inbox placement, and a rapid decline in sender reputation. My goal is to outline the key deliverability and compliance tools and practices every new ESP should prioritize for sustained success.
Robust authentication and infrastructure
Email authentication is the bedrock of deliverability and compliance. SPF, DKIM, and DMARC are non-negotiable standards that verify sender identity and help prevent spoofing and phishing. For a new ESP, providing seamless setup for these protocols is critical.
Every client account should have dedicated or custom return/bounce domains and click tracking domains configured. This ensures that all parts of an email, from the sender address to tracking links, are properly authenticated under the client’s domain. This practice significantly improves trust with receiving mail servers.
Automated DMARC alerts are also incredibly valuable. Imagine a system that checks a client’s DMARC policy before a send and warns them if their email is likely to fail authentication. This proactive approach can prevent significant deliverability issues before they even occur.
Authentication protocols
Every email must be authenticated using SPF, DKIM, and DMARC. Implement these for all sending domains.
SPF: Publish a Sender Policy Framework (SPF) record to list authorized sending IP addresses and domains.
DKIM: Set up DomainKeys Identified Mail (DKIM) to digitally sign outgoing emails, providing a tamper-proof verification.
DMARC: Implement Domain-based Message Authentication, Reporting, and Conformance (DMARC) to tell receiving servers how to handle emails that fail SPF or DKIM checks, and to receive DMARC reports.
Monitoring and reputation management
Proactive monitoring is non-negotiable for a new ESP. This includes vigilant observation of IP and domain reputation across major blocklists (also known as blacklists). Tools that offer real-time blocklist monitoring are essential to quickly identify and address any listing issues. Internal use of blocklists like Spamhaus is crucial; don't allow clients to send from domains that are already listed.
Leveraging postmaster tools from major mailbox providers is also vital. Services like Google Postmaster Tools and Outlook SNDS provide invaluable insights into your sending reputation, spam rates, and DMARC failures. Integrating this data into your internal monitoring systems allows for proactive alerts and rapid response to emerging issues.
Regular email deliverability testing is another key practice. Using an email deliverability tester can help assess inbox placement across various mailbox providers, identifying potential issues with content or infrastructure before they impact live campaigns. Periodic checks using tools like Mail-Tester can also provide a snapshot of your infrastructure's default state.
Blocklist monitoring
Actively monitor major public blocklists and private blacklists. Utilize services that provide real-time alerts for IP and domain listings. This allows for immediate action if a sending reputation is compromised.
Reputation tracking
Integrate data from Google Postmaster Tools and Outlook SNDS (Smart Network Data Services). Set up automated alerts for changes in IP and domain reputation, spam rates, and other key metrics. Overlaying email volume with this data helps pinpoint issues.
Internal compliance and abuse management
Compliance is more than just avoiding blocklists; it's about adhering to legal requirements and ethical sending practices. A new ESP needs robust internal mechanisms to enforce compliance across all client accounts. This starts with a thorough vetting process for new prospects, including a discovery checklist that identifies red flags before onboarding.
It's essential to implement an internal system similar to Mailchimp's Omnivore, which can proactively identify problematic content or sending patterns. This system should continuously stack-rank clients based on internal metrics, such as high bounce and complaint rates or low engagement. This allows the ESP to target areas for compliance intervention effectively. Preventing bad actors from joining or quickly identifying and managing them is key to protecting shared IP reputation.
Furthermore, an ESP needs a dedicated abuse or compliance desk, staffed with deliverability experts who have developer and data analyst support. This team should operate independently from customer support management to ensure unbiased decision-making regarding compliance issues and client account actions. This organizational structure emphasizes the importance of maintaining a clean sending environment above all else.
Example compliance workflow for new client onboarding
A new ESP should implement a stringent compliance workflow to protect its sender reputation. Here is an example of such a process:
Pre-screening: Sales teams use a checklist to vet prospects for potential red flags and gather necessary compliance information.
Automated content scanning: Automated systems scan email content and lists for known spam triggers or blocklisted (blacklisted) domains before sending.
Performance monitoring: Continuously monitor client sending behavior, focusing on bounce rates, complaint rates, and engagement metrics.
Tiered response: Implement escalating responses for non-compliant clients, from warnings to sending restrictions or account termination.
Feedback loops: Subscribe to feedback loops (FBLs) from major ISPs to receive notifications about spam complaints and take action on senders.
Additional tools and practices
To support both deliverability and compliance, a new ESP should consider several additional tools and features. These often integrate with existing systems or provide specialized insights crucial for maintaining a healthy sending ecosystem.
A comprehensive email validation tool should be integrated at the point of list entry. This prevents sending to invalid, risky, or spam trap addresses, which are major contributors to poor deliverability and blacklisting. Real-time validation at capture points is ideal.
Finally, a customized unsubscribe page with a feedback form can provide invaluable insights into why subscribers are leaving. Offering options like "no longer want these emails," "never signed up," or "these emails are spam" can help an ESP better understand engagement issues and refine sending practices. This feedback helps prevent future complaints and improves overall list hygiene, reducing the likelihood of being placed on a blocklist or blacklist.
Views from the trenches
Best practices
Implement automated systems to scan client email content for spam triggers and blocklisted domains.
Establish a clear client vetting process with red flag warnings before onboarding.
Empower your abuse/compliance desk with developer and data analyst support, keeping them separate from customer support management.
Ensure SPF, DKIM, and DMARC are correctly configured for all client sending domains to maximize deliverability.
Common pitfalls
Allowing sales teams to onboard high-risk clients without a rigorous compliance review.
Not having real-time alerts for IP or domain blacklisting, leading to delayed issue resolution.
Failing to collect and act on granular unsubscribe feedback from recipients.
Lacking a system to actively monitor and surface Postmaster Tools data for clients.
Expert tips
Consider clawback provisions for sales commissions on accounts terminated due to compliance issues within a certain period (e.g., 6-12 months).
Develop an internal system similar to Mailchimp’s Omnivore for proactive content and sending pattern analysis.
Provide automated DMARC alerts to clients upon test sends if their email is likely to fail authentication.
Enforce that no side letters modify standard contracts, protecting against unforeseen contractual obligations.
Marketer view
A marketer from Email Geeks says that a platform integrated with Postmaster Tools and SNDS data, which surfaces reputation data, is crucial because building that manually can be challenging.
2023-12-12 - Email Geeks
Marketer view
A marketer from Email Geeks suggests that a discovery checklist for sales to vet prospects before onboarding is essential, including red flag warnings based on prospect responses or lack thereof.
2023-12-12 - Email Geeks
Building a solid foundation for email success
For a new ESP, setting up a solid foundation of deliverability and compliance tools isn't just a best practice, it's a survival strategy. By prioritizing robust authentication, proactive monitoring, and stringent internal compliance, an ESP can build a strong sender reputation from day one.
The initial investment in these areas, from technical infrastructure to dedicated compliance teams, will pay dividends by ensuring high inbox placement rates and preventing costly blacklistings (or blocklistings) and reputation damage. This commitment to deliverability and compliance helps new ESPs navigate the complex email ecosystem effectively.
Outlook SNDS provide invaluable insights into your sending reputation, spam rates, and DMARC failures. Integrating this data into your internal monitoring systems allows for proactive alerts and rapid response to emerging issues.
