Why are my emails going to spam after IP warming despite good domain reputation?
Matthew Whittaker
Co-founder & CTO, Suped
Published 15 May 2025
Updated 16 Aug 2025
7 min read
It's a perplexing scenario: you've diligently warmed up your IP address, your domain reputation appears solid, yet your emails consistently land in the spam folder. This is a common frustration for senders, especially those transitioning from shared IP environments to dedicated ones, or scaling their email operations.
The assumption that a good domain reputation automatically confers trust upon a new, dedicated IP address is a misconception. While your domain's established history is certainly a factor, mailbox providers (like Google and Yahoo) also maintain a separate, independent reputation score for each sending IP. This score is built over time based on sending behavior from that specific IP address.
The challenge is that new IP addresses are inherently viewed with suspicion until they demonstrate consistent, positive sending patterns. This initial skepticism, even with a strong domain reputation, can lead to emails being directed to the spam or junk folder. Let's delve into the core reasons behind this issue and how to address them.
IP reputation versus domain reputation
Even with an established domain, a new dedicated IP address essentially starts with a neutral, or even slightly negative, reputation. Mailbox providers monitor sending volume, bounce rates, spam complaints, and engagement metrics specifically for that IP. If the warming process isn't carefully executed, or if initial sending patterns raise red flags, it can quickly lead to blocklisting (or blacklisting) or direct-to-spam routing.
While your domain reputation acts as a long-term trust signal, the IP reputation is more dynamic and susceptible to recent sending behavior. For example, if you quickly ramp up volume on a new IP, even with a good domain, it can appear suspicious to ISPs who prefer to see a gradual increase, as outlined by Postmark's guide on domain warming.
The interplay between these two reputations is critical. A strong domain reputation can somewhat mitigate a new IP's lack of history, but it won't entirely override a poor or unestablished IP reputation. Mailbox providers consider both to determine overall sender trustworthiness, as highlighted by Twilio's explanation on email reputation basics.
Technical configuration beyond authentication
Beyond the IP itself, the underlying technical configuration of your sending infrastructure plays a massive role. Even if your SPF, DKIM, and DMARC records appear perfect, there are often subtle misconfigurations that can trip up spam filters. These include issues with Reverse DNS (rDNS), the HELO/EHLO command, and the origin or neighborhood of your IP address.
A common oversight is incorrect or missing rDNS setup. rDNS allows recipient servers to look up the hostname associated with your sending IP address. If this doesn't match your HELO/EHLO greeting (the hostname your sending server announces itself as), it can be a significant red flag, signaling a potential spoofing attempt or misconfiguration. Ensure your rDNS record resolves to the correct hostname, and that your Mail Transfer Agent (MTA) is configured to use this hostname in its HELO/EHLO greeting.
Furthermore, the history of your newly acquired IP address matters. If the IP was previously used for spamming, it might be listed on various public or private blocklists (blacklists), making it hard to achieve inbox placement. Even if the specific IP isn't blocklisted, the reputation of the larger IP block it belongs to (its neighbors) can negatively influence its deliverability. Investigate the IP's history before committing to it.
Checking your technical setup
To troubleshoot these technical aspects, use tools that can verify your rDNS, HELO, and IP block reputation. Pay close attention to what your Mail Transfer Agent (MTA) is announcing itself as during the initial connection.
Reverse DNS (rDNS): Verify that your sending IP has a properly configured rDNS record that points back to your domain.
HELO/EHLO Greeting: Ensure your MTA is configured to use a fully qualified domain name (FQDN) in its HELO/EHLO greeting that matches your rDNS.
IP Block Reputation: Check if other IPs in your assigned block have poor reputations, as this can affect yours by association.
Content quality and engagement
Even with perfect IP warming and technical setup, email content and recipient engagement are paramount. Spam filters continuously analyze email content for suspicious keywords, formatting, and link patterns. A sudden shift in content style from what your domain previously sent, or even sending plain text emails with common spam triggers, can lead to filtering.
Engagement metrics are increasingly vital for inbox placement. Mailbox providers track how recipients interact with your emails: opens, clicks, replies, and whether they mark your emails as spam or move them to the junk folder. If initial sends from the new IP receive low engagement or high complaint rates, it will negatively impact the IP's reputation, overriding any positive domain reputation you may have.
Ensure your list is clean and actively engaged. Sending to inactive or invalid email addresses can trigger spam traps or generate bounces, both of which harm your sender reputation. A high number of unsolicited spam complaints, even from a small percentage of recipients, is a strong signal to ISPs that your emails are unwanted.
Content pitfalls
Spammy language: Overuse of all caps, exclamation points, vague subject lines, or salesy jargon.
Broken formatting: Poor HTML, excessive images relative to text, or suspicious links.
Inconsistent content: Shifting drastically from your usual email content or brand voice.
Engagement strategies
List hygiene: Regularly clean your list of inactive or invalid addresses to avoid bounces and spam traps.
Segmentation: Send highly relevant content to engaged segments of your audience first.
Feedback loops: Implement feedback loops with ISPs to quickly identify and remove complainers.
Refining the IP warming strategy
Despite having a well-planned IP warming strategy, sometimes the process itself needs adjustment. It's not just about sending *some* emails, but sending the *right* volume and type of emails to the *right* recipients at the *right* pace. Too fast, and you look like a spammer. Too slow, and you don't build sufficient positive signals.
One common issue is sending very low-volume test messages. While individual tests might show a perfect setup, ISPs often require a certain volume of positive engagement to truly build trust for a new IP. A few test emails, even if clean, might not provide enough data for filters to greenlight your IP, especially if it's never been used before. This is particularly true when migrating from a large-scale provider like Amazon SES to a new dedicated IP, as the transition involves establishing a fresh reputation from scratch.
Continuously monitor your deliverability during and after IP warming. Use Google Postmaster Tools and other available analytics to track your IP reputation, spam complaint rates, and engagement. If you see emails going to spam (junk folder) at specific providers, adjust your sending volume or content for those providers.
The path to better deliverability
Successfully warming an IP and maintaining inbox placement is a dynamic process that requires attention to multiple factors. A strong domain reputation is a great asset, but it does not guarantee immediate trust for a new IP. Focus on a meticulously planned warming schedule, ensure your technical configurations are flawless, maintain highly engaged recipient lists, and continuously monitor your deliverability metrics to identify and address issues promptly.
Views from the trenches
Best practices
Always ensure your rDNS is correctly configured for your sending IP and matches your HELO/EHLO greeting.
Segment your audience and begin IP warming with your most engaged subscribers who are likely to open and click.
Gradually increase your sending volume over weeks or months, following recommended IP warming schedules.
Regularly monitor your IP reputation and spam complaint rates through Postmaster Tools and other services.
Common pitfalls
Assuming good domain reputation automatically transfers to a new IP, leading to aggressive sending volumes.
Neglecting to check the historical reputation or the 'neighborhood' of your newly acquired IP address.
Not thoroughly verifying all technical configurations, including rDNS and HELO/EHLO settings.
Sending emails with inconsistent content or to unengaged lists during the critical warming period.
Expert tips
Verify your rDNS and HELO/EHLO hostname alignment. Mismatches are a major red flag for ISPs.
If migrating from an ESP, ensure all authentication records (SPF, DKIM, DMARC) are correctly transferred and configured for your new setup.
Consider starting with transactional emails first, as they typically have higher engagement rates.
Be patient. Building a solid IP reputation takes consistent, positive sending over time, especially for high volumes.
Expert view
Expert from Email Geeks says it takes time to build a sending reputation with a dedicated IP, which is why a warmup plan is essential. Very low volume test messages may be insufficient signals for filters.
2022-07-08 - Email Geeks
Expert view
Expert from Email Geeks says that when moving from an ESP to your own setup, troubleshooting technical configurations such as rDNS, HELO, the IP source, and upstream ASN is crucial.
Amazon SES to a new dedicated IP, as the transition involves establishing a fresh reputation from scratch.
