What are the best practices for email deliverability when using SparkPost and Amazon SES, including reverse DNS, blacklist monitoring, and handling dedicated IPs?
When you're leveraging third-party email service providers (ESPs) like SparkPost and Amazon SES, some of the technical heavy lifting, such as IP reputation and infrastructure management, falls to them. However, it's still crucial to understand your responsibilities and how to optimize your sending practices to ensure your emails reliably reach the inbox.
This guide will walk you through the essential best practices, focusing on areas you control and how to collaborate effectively with your ESP to maximize deliverability, especially when using dedicated IPs and navigating the complexities of email blocklists (or blacklists).
Dedicated IP addresses offer more control over your sending reputation compared to shared IPs. With a dedicated IP, your sending behavior directly impacts its reputation, making it essential to manage carefully. Both SparkPost and Amazon SES allow the use of dedicated IPs, and understanding how to warm them up and maintain their health is paramount. IP warming is a critical process where you gradually increase your sending volume over time, allowing mailbox providers to assess your sending patterns and build trust. Without proper warm-up, your emails are more likely to be flagged as spam or rejected.
When you use dedicated IPs from an ESP, they handle the underlying infrastructure. However, you are responsible for the quality of the email you send through those IPs. This includes maintaining clean recipient lists, avoiding spam traps, and ensuring your content is engaging and relevant. If your dedicated IP ends up on a blocklist, it directly impacts your email deliverability, and swift action is required. Your ESP will often provide tools or dashboards to help you monitor your IP reputation.
I’ve found that using dedicated IPs is beneficial if your sending volume is consistently high and your email program is stable. For volumes less than 300,000 messages per month, a shared IP pool might be sufficient as the ESP automatically manages the reputation across many senders. However, for higher volumes or specific use cases requiring strict control, dedicated IPs are the way to go. SparkPost provides an IP warm-up strategy overview that can guide your process.
Shared IP Considerations
Reputation shared: Your sending reputation is influenced by other users on the same IP.
Less control: You have minimal influence over rDNS or blacklist status.
Cost-effective: Often cheaper for lower volumes.
Setting up reverse DNS
Reverse DNS (rDNS) is a crucial authentication mechanism that verifies the IP address of an email sender matches its designated domain name. It’s like a digital caller ID for your email server. When using SparkPost or Amazon SES, especially with dedicated IPs, ensuring proper rDNS setup is vital for establishing trust with recipient mail servers. Mailbox providers often check for rDNS to validate legitimacy, and a mismatch or missing rDNS can raise red flags, potentially leading to emails being marked as spam or rejected.
For IPs you control directly in your own datacenter, you absolutely should configure reverse DNS entries. The rDNS (PTR record) should ideally resolve to a hostname that aligns with your sending domain, for example, mail.yourdomain.com. If you're sending for multiple customers or domains from the same IPs, you'll need to work with your ISP or hosting provider to set up the PTR records. You might choose a generic but descriptive hostname, or, if possible, align it with the primary domain associated with that IP's traffic.
When using SparkPost or Amazon SES for sending, if you are leveraging their dedicated IPs, they are responsible for configuring the rDNS. However, it's a good practice to confirm this setup with them. Typically, their dedicated IPs will have rDNS records that resolve to their own service domains, which is perfectly acceptable. If you are using your own IPs but routing mail through their services (e.g., via a custom MTA setup that then relays to SparkPost/SES), ensure that your own IPs have valid rDNS set up on your end.
Blacklist monitoring strategy
Email blacklists (or blocklists) are databases of IP addresses or domains that have been identified as sources of spam or malicious email. While some blacklists carry significant weight and can severely impact your deliverability, many are less influential. It's a common misconception that you need to monitor every single blacklist. Instead, focus on the major ones and prioritize other deliverability metrics.
The most important blacklist to watch out for is Spamhaus. Getting listed by Spamhaus will almost immediately cause significant deliverability issues with major mailbox providers. If you are sending from your own IPs, you should actively monitor them for listings on Spamhaus and a few other key reputation databases. Tools exist that can check multiple blacklists simultaneously, such as multirbl.valli.org.
If you are using SparkPost's or Amazon SES's IPs (either shared or dedicated), the primary responsibility for monitoring their IPs and addressing blacklist issues lies with them. They have dedicated teams and sophisticated systems in place for this. Your focus should be on maintaining good sending practices, ensuring your emails are legitimate, and monitoring the deliverability metrics provided by the ESP. Should a dedicated IP get blocklisted, your ESP will usually work with you to remediate the issue, as their reputation is also at stake.
Key Blacklists to Monitor
Spamhaus: Highly influential, a listing here demands immediate attention and remediation.
URIBL: Lists domains found in spam, important for link reputation.
Others: Many smaller lists exist, but their impact is usually localized.
While blocklist monitoring is a piece of the puzzle, it's not the entire solution. Focus more on preventing issues in the first place by adhering to best practices like proper email authentication (SPF, DKIM, DMARC), maintaining healthy sending practices, and monitoring your ESP’s provided metrics closely. These proactive steps are far more effective in ensuring long-term deliverability than reactive blacklist checks. Amazon SES offers guidance on navigating bulk sender requirements, which includes robust authentication setup.
Maintaining overall sender reputation
Beyond the specific technical configurations like rDNS and IP management, your overall deliverability success hinges on a broader set of best practices. These include maintaining a clean and engaged subscriber list, sending relevant content, and actively monitoring your sender reputation through various channels. Both SparkPost and Amazon SES provide sophisticated analytics and dashboards that give you insight into your sending performance, including bounce rates, complaint rates, and open rates. Pay close attention to these metrics, as they are early indicators of potential issues.
High bounce rates, especially hard bounces, indicate invalid email addresses that should be removed from your list promptly. High complaint rates (spam reports) are a strong signal that your recipients are not happy with your emails, which can severely damage your reputation. Regularly cleaning your list, implementing double opt-in, and providing clear unsubscribe options are fundamental practices. Monitoring bounces and comparing open rates is key to effective deliverability management.
Leverage tools provided by ESPs, like SparkPost's Delivery Index, to get a holistic view of your email program’s health. Don't solely rely on external tools for basic checks; your ESP's internal reporting is often the most accurate reflection of how your emails are performing with major mailbox providers.
Proactive Deliverability Measures
List hygiene: Regularly remove inactive or bouncing addresses.
Content quality: Ensure your email content is relevant and not spammy.
Actively manage and warm up your dedicated IPs if you're sending high volumes, gradually increasing traffic to build reputation.
Ensure that all IPs appearing in your email headers (even those from your own datacenter) have correctly configured reverse DNS records.
Prioritize monitoring key deliverability metrics provided by your ESP, such as bounce rates and complaint rates, as primary indicators of health.
Implement strong email authentication (SPF, DKIM, DMARC) for all your sending domains to build trust with mailbox providers.
Regularly clean your email lists to remove inactive users and hard bounces, which helps prevent blacklisting and improves engagement.
Common pitfalls
Over-relying on generic blacklist checks, as many blacklists are not influential enough to significantly impact deliverability.
Neglecting the warm-up process for new dedicated IPs, which can lead to immediate filtering or rejections by ISPs.
Ignoring the specific metrics and dashboards provided by SparkPost or Amazon SES, which offer the most accurate insights into your performance.
Failing to configure reverse DNS for IPs that you control, causing suspicious flags for receiving mail servers.
Assuming that once you hand off sending to an ESP, all deliverability concerns are automatically handled without your involvement.
Expert tips
The most impactful blacklist is Spamhaus; focus your attention there, as a listing will be immediately apparent through other metrics.
Consider other less influential blocklists as an early warning system, indicating underlying issues that need addressing.
If using dedicated IPs from an ESP, discuss reverse DNS configuration with them; for shared IPs, it's generally out of your control.
When using an ESP, their provided metrics and dashboards are your most valuable resources for day-to-day deliverability monitoring.
Proactive list hygiene and content relevance are far more effective than reactive blacklist removals for long-term inbox placement.
Expert view
Expert from Email Geeks says that monitoring most blacklists is a waste of time, as more important metrics should be prioritized.
September 6, 2023 - Email Geeks
Expert view
Expert from Email Geeks says that reverse DNS should ideally match the hostnames of your machine and the EHLO name, as some filters are wary of generic or missing reverse DNS.
September 6, 2023 - Email Geeks
Final thoughts
Achieving excellent email deliverability with SparkPost and Amazon SES, especially at high volumes and with dedicated IPs, requires a blend of technical diligence and strategic sending practices. Focus on the areas you directly control, such as list hygiene, content quality, and proper authentication (SPF, DKIM, DMARC).
For elements like rDNS on dedicated IPs and the majority of blacklist monitoring, rely on your ESP’s expertise and robust reporting tools. By understanding these best practices and maintaining a collaborative relationship with your email service provider, you can navigate the complexities of email deliverability and consistently reach your recipients’ inboxes.
Spamhaus
0Spam
Cisco
NoSolicitado
URIBL
abuse.ro
ALPHANET
Anonmails
Ascams
BLOCKEDSERVERS
Calivent Networks
EFnet
JustSpam
Kempt.net
NordSpam
RV-SOFT Technology
Scientific Spam
Spamikaze
SpamRATS
SPFBL
Suomispam
System 5 Hosting
Team Cymru
Validity
www.blocklist.de Fail2Ban-Reporting Service
ZapBL
2stepback.dk
Fayntic Services
ORB UK
technoirc.org
TechTheft
Spamhaus. Getting listed by Spamhaus will almost immediately cause significant deliverability issues with major mailbox providers. If you are sending from your own IPs, you should actively monitor them for listings on Spamhaus and a few other key reputation databases. Tools exist that can check multiple blacklists simultaneously, such as multirbl.valli.org.
