Summary
Migrating from a well-established email service provider (ESP) like Amazon SES to a dedicated IP address can introduce unexpected deliverability challenges, even when your domain reputation is strong and authentication records are perfectly configured. While a high domain reputation on platforms like Gmail Postmaster Tools indicates trust in your sending domain, a new or newly warmed IP address still needs to build its own independent reputation with internet service providers (ISPs). This summary explores why emails might go to spam despite seemingly ideal conditions and highlights the critical factors involved.
Key findings
- IP reputation: A new dedicated IP address starts with a neutral or unknown reputation, irrespective of your domain's established standing. ISPs need time and consistent positive sending behavior to trust a new IP, making it prone to initial spam folder placement.
- Low volume during warming: Very low volume test messages during the initial warming phase might not provide sufficient positive signals to mailbox providers, leading them to classify emails as spam. Gradual, consistent volume increases are crucial.
- Technical configuration: Issues with rDNS, HELO settings, or even the IP's previous history (if it's not a truly pristine IP) can trigger spam filters. These technical details are often managed by ESPs, becoming a sender's responsibility with dedicated IPs.
- Domain vs. IP reputation interplay: While domain reputation is highly influential, a new IP's reputation must be built independently, and a strong domain cannot fully compensate for a weak or unproven IP reputation. For more on this, see Twilio's explanation of IP vs. Domain Reputation.
Key considerations
- Comprehensive IP warming strategy: A detailed plan with gradually increasing volumes sent to engaged recipients is essential to establish a positive IP reputation. Consistency is key, even if initial results are challenging.
- Technical audit: Thoroughly check all technical configurations, including rDNS, HELO, and ensure proper SPF, DKIM, and DMARC alignment. Even minor misconfigurations can lead to deliverability issues.
- IP history assessment: Investigate the history of the dedicated IP address before committing to it. A previously abused IP can be difficult to rehabilitate. You can check this using a blocklist checker.
- Patience and persistence: Building IP reputation takes time. It's not uncommon for deliverability to fluctuate during the warming period. Sticking to the plan and continuously monitoring metrics is vital.
What email marketers say
Email marketers often face the dilemma of achieving inbox placement when transitioning to a dedicated IP, even with a stellar domain reputation from an existing ESP. Their experiences highlight the nuances of IP warming and the common pitfalls that can lead to emails landing in the spam folder. They emphasize that while domain reputation is crucial, a new IP must still earn its stripes with ISPs through careful and consistent sending practices.
Key opinions
- IP reputation is distinct: Many marketers acknowledge that IP reputation is a separate entity from domain reputation. Even if your domain has a strong history, a new IP starts from scratch and requires a dedicated warming process.
- Low test volume issues: Initial test sends, especially if very low in volume, may not provide enough positive engagement signals to ISPs, causing them to default to spam folder placement during warming.
- ESP vs. self-managed complexities: Marketers moving from managed ESPs (like SES) to self-managed setups (e.g., Greenarrow MTA) often encounter new technical considerations that were previously handled by the ESP, such as rDNS and HELO configuration.
- Patience is key: Despite doing everything right, including SPF, DKIM, and DMARC, deliverability during warming can be inconsistent. Persistence and adhering to the warming plan are often cited as critical for eventual success.
Key considerations
- Warm-up carefully: Implement a structured warm-up plan with gradual volume increases to help ISPs build trust in the new IP. Sending too much too soon, or too little, can both hinder progress.
- Verify technical configurations: Double-check all DNS settings, particularly rDNS, HELO records, and ensure proper SPF, DKIM, and DMARC authentication are in place and aligned. These are common culprits for deliverability issues.
- Monitor spam rates: Continuously monitor your spam rates and adjust sending volume accordingly. Even low spam rates can cause problems if they occur consistently on a new IP.
- Understand IP history: Be aware that the history of your chosen IP address can significantly impact initial deliverability. An IP with a poor past reputation (a blocklisted or blacklisted IP) will be harder to warm up. Learn more in this Mailgun article on avoiding spam.
Marketer view
Email marketer from Email Geeks states that even with low spam rates and high domain reputation, testing emails on a new dedicated IP often go straight to spam, despite having another high-volume IP in the same range with 100% inbox placement. This suggests that the issue might be specific to the newly chosen IP or its warming process, indicating that a new IP doesn't automatically inherit the domain's established reputation.
Marketer view
Email marketer from Email Geeks suggests that building a sending reputation with a dedicated IP takes time, emphasizing the necessity of a proper warm-up plan. They point out that very low volume test messages might provide insufficient signals to spam filters, leading to immediate spam placement, and advises checking email authentication (SPF, DKIM, or DMARC).
What the experts say
Email deliverability experts highlight that while domain reputation is crucial, it does not entirely supersede the need for a dedicated IP to establish its own trustworthiness. They emphasize the importance of granular technical configurations and the overall ecosystem surrounding the IP address. A blocklist entry or a misconfigured technical aspect can quickly negate the benefits of a good domain reputation, particularly for a new sending IP.
Key opinions
- Technical deep dive required: Experts commonly point to technical configurations like rDNS, HELO settings, and the origin of the IP address (e.g., if it was previously SWIPed) as primary areas to troubleshoot when a new IP struggles with deliverability.
- IP neighborhood matters: The reputation of neighboring IPs (other senders on the same subnet or ASN) can affect a new IP's initial standing with ISPs, even if the domain is clean.
- Beyond authentication: While SPF, DKIM, and DMARC are foundational, experts suggest that even with perfect authentication, other factors like IP reputation and sender behavior during warming play a significant role in deliverability.
- Transition from ESP to self-hosted: Experts note that the challenges of troubleshooting deliverability often arise when senders transition from a managed ESP environment (where many technical details are abstracted) to a self-managed setup using a dedicated MTA and IP.
Key considerations
- Detailed IP investigation: Before warming, thoroughly investigate the IP's history, its previous usage, and any associated blacklist or blocklist records.
- Verify full DNS setup: Ensure rDNS is correctly configured for your dedicated IP and matches your HELO name. Incorrect rDNS is a common red flag for ISPs.
- Understand the IP provider: Investigate who owns the IP (e.g., is it SWIPed to you) and the reputation of the upstream Autonomous System Number (ASN) provider, as this can impact trust.
- Patience and data-driven adjustments: Building IP reputation is a gradual process that requires careful monitoring of deliverability metrics and adjusting sending volumes based on ISP feedback. Review this article on improving IP reputation.
Expert view
Expert from Email Geeks suggests that when moving from an ESP to a self-managed setup, various technical aspects that were previously handled automatically become the sender's responsibility. These include rDNS, HELO settings, the source of the IP, and understanding the network neighbors, all of which are crucial starting points for troubleshooting deliverability issues.
Expert view
Expert from Email Geeks confirms that they do not definitively believe the issue is solely the IP, but rather that examining technical configurations like rDNS, HELO, and IP source are the first steps in troubleshooting. This indicates a holistic approach to deliverability, where many factors contribute beyond just the IP itself.
What the documentation says
Technical documentation and industry guides provide a structured understanding of how IP and domain reputations are formed and interact. They underline that while domain reputation is crucial for brand identity and overall sender trustworthiness, ISPs also independently assess the reputation of the originating IP address. This dual evaluation means that even with a strong domain, a new or unproven IP can be treated with caution, leading to emails being filtered to spam.
Key findings
- Separate reputation scores: Most documentation confirms that ISPs maintain separate reputation scores for both sending IP addresses and domains. While related, a good domain reputation does not automatically transfer to a new or unproven IP.
- Importance of authentication: Proper configuration of SPF, DKIM, and DMARC is fundamental for any sending setup. Documentation stresses that authentication failures are a primary reason for emails to be flagged as spam, regardless of IP or domain reputation history.
- IP warming protocols: Official guidelines for IP warming typically recommend a slow, gradual increase in sending volume, starting with highly engaged recipients. This methodical approach helps build trust and establish a positive sending history for the new IP.
- Feedback loops and blocklists: Documentation often highlights the role of spam complaints (via feedback loops) and blocklists (or blacklists) as key indicators of poor sender behavior, which can immediately damage a new IP's reputation.
Key considerations
- Adhere to warming schedules: Follow recommended warming schedules and best practices strictly. Deviating from these can lead to slower reputation building or immediate filtering.
- Technical compliance is non-negotiable: Ensure all DNS records, including SPF, DKIM, DMARC, and rDNS, are correctly configured and aligned with your sending practices. Review EmailTooltester's fixes for emails going to spam.
- Monitor blocklists: Regularly check your new IP address against major public blacklists to identify and address any issues promptly.
- Content quality: Even with a good IP and domain, poor content (e.g., spammy keywords, suspicious links, low text-to-image ratio) can trigger filters, especially during the sensitive warming period.
Technical article
Documentation from SecurityScorecard explains that with IP warming, senders gradually increase email volume over time, starting with small amounts. This process is crucial because if a large volume of email is sent from a new IP, ISPs will likely flag it as suspicious and direct it to spam folders.
Technical article
Documentation from Twilio outlines that domain reputation, linked to a brand's website, often takes precedence in ISP filtering decisions. However, the email's reputation score is also significantly influenced by the quality of email from other senders sharing the same IP address, creating a shared responsibility.
Related resources
13 resources
Related pages
What causes emails to go to spam when migrating to a new ESP and warming an IP?
Why are emails from new dedicated IPs and domains landing in spam?
How important is email warming on shared IPs, and how do domain and IP reputations interact?
Why Your Emails Are Going to Spam in 2024 and How to Fix It
How email blacklists actually work: a simple guide
What happens when your ip gets blocklisted?
A simple guide to DMARC, SPF, and DKIM
Boost Email Deliverability Rates: Technical Solutions from Top Performing Senders
How to Improve Domain Reputation Using Google Postmaster Tools [2025 Guide]
Why are my emails being marked as spam even with good domain reputation?
