Summary
Even with good open rates during a new subdomain warmup, emails may still land in the spam folder due to numerous interconnected factors. Experts and documentation emphasize that sender reputation, heavily influenced by spam complaints, spam trap hits, engagement metrics, and sending practices, plays a central role. Inadequate list hygiene, aggressive or inconsistent warmup schedules, and spam-triggering content can damage this reputation. Additionally, technical aspects such as misconfigured authentication, shared EPS domain links, blacklisted IPs, and poor image-to-text ratios contribute to deliverability issues. The age of the domain and the type of IP address are also important to consider. Seed list results may not accurately reflect real-world deliverability, making comprehensive monitoring crucial.
Key findings
- Sender Reputation is Key: A low sender reputation, even with proper authentication, is a primary cause of spam folder placement.
- Engagement Matters More Than Opens: ISPs prioritize engagement metrics such as click-through rates, replies, and forwards over open rates.
- Content Can Trigger Spam Filters: Spam filters analyze email content for trigger words, poor image-to-text ratios, and suspicious links.
- List Quality Impacts Reputation: Poor list hygiene, resulting from unengaged subscribers and improper acquisition methods, damages sender reputation.
- Warmup Strategy is Critical: Aggressive or inconsistent warmup schedules raise red flags with ISPs and negatively impact deliverability.
- Links Matter: Links to shared EPS domains, rather than your own, can damage your domain reputation.
- IP and Domain Blacklisting: A blacklisted IP or domain will severely hamper deliverability.
Key considerations
- Establish a Gradual Warmup: Implement a slow, consistent warmup schedule, increasing sending volume gradually.
- Prioritize Engagement: Focus on sending to engaged subscribers and creating compelling content that encourages clicks and interaction.
- Optimize Email Content: Avoid spam trigger words, maintain a balanced image-to-text ratio, and use a custom tracking domain.
- Maintain List Hygiene: Regularly remove unengaged subscribers and implement a double opt-in process to build a clean, engaged list.
- Authenticate Properly: Ensure SPF, DKIM, and DMARC are correctly configured to authenticate your sending domain.
- Monitor Reputation and Blacklists: Continuously monitor your domain and IP reputation and address any blacklisting issues promptly.
- Review link usage: Ensure all links point to the sender's own domain, not shared EPS domains.
- Consider IP address type: Shared IPs often have bad reputations. Consider a dedicated IP address.
- Domain Age: Consider the implications a new domain has on its initial sending reputation.
What email marketers say
13 marketer opinions
Even with good open rates, emails may land in the spam folder during subdomain warmup due to factors beyond initial engagement. Aggressive warmup schedules, poor list hygiene, content triggering spam filters, inconsistent sending patterns, and blacklisting can negatively impact deliverability. ISPs prioritize engagement metrics beyond opens, such as click-through rates and replies. Subdomain and IP reputation, including past blacklisting, play a crucial role. Double opt-in processes and good image-to-text ratios are important factors. Proper sender authentication is a necessity, but not a guarantee. The domain age and the IP address type (shared or dedicated) are also considerations.
Key opinions
- Warmup Schedule: Aggressive warmup schedules with rapid volume increases can trigger spam filters, despite initial high open rates.
- Engagement: ISPs evaluate engagement metrics beyond open rates, prioritizing click-through rates, replies, and forwards.
- Content Triggers: Spam filters analyze email content for trigger words, excessive capitalization, and other spam-like characteristics.
- Reputation: Subdomain and IP reputation, including past blacklisting, significantly impact deliverability during warmup.
- List Quality: Poor list hygiene, including unengaged subscribers and purchased lists, leads to spam complaints and harms sender reputation.
Key considerations
- Gradual Warmup: Implement a gradual warmup schedule with slow, consistent increases in sending volume.
- Engagement Focus: Segment your list to prioritize sending to engaged subscribers with high click-through rates and replies.
- Content Optimization: Optimize email content to avoid spam triggers, maintain a good image-to-text ratio, and use a custom tracking domain.
- Reputation Monitoring: Monitor subdomain and IP reputation for blacklisting and address any issues promptly.
- List Hygiene Practices: Regularly clean your email list to remove unengaged subscribers and implement a double opt-in process to ensure genuine interest.
- Domain Age: Consider that a newer domain may have lower trust until it establishes a good history.
- IP Address: Consider using Dedicated IP addresses over Shared as they are cleaner and you have control.
Marketer view
Email marketer from Email Geeks shares that it's common for mail streams to land in the spam folder when new, as Gmail wants to see users moving mail from spam to inbox. Reducing volume and sending regularly can improve inbox placement, but it takes time to show results. Alison also notes that Gmail may not report spam complaints on low volumes of messaging, so the absence of reports isn't definitive proof of no complaints.
30 Nov 2023 - Email Geeks
Marketer view
Email marketer from Email Geeks explains that doubling volume each day can be too aggressive for warming up and recommends increasing volume by 20-30% per day. Sending once a day and using send time optimization is also recommended.
6 Oct 2024 - Email Geeks
What the experts say
5 expert opinions
During subdomain warmup, even with good open rates, emails can land in the spam folder due to several expert-identified factors. Links pointing to shared EPS domains, rather than the sender's own domain, can trigger spam filters. Low sending volume might prevent the establishment of a positive reputation. Methods of list acquisition, such as co-registration, can lead to low-quality addresses and spam complaints. ESPs and ISPs are highly sensitive to negative signals during warmup due to the lack of established reputation. Seed list results may not accurately reflect real-world inbox placement.
Key opinions
- Shared Domains: Links to shared EPS domains negatively impact deliverability.
- Low Volume: Insufficient sending volume hinders the establishment of a positive reputation.
- List Acquisition: Poor list acquisition methods (co-reg, incentives) lead to low-quality addresses and spam complaints.
- New Reputation: New subdomain reputations are highly vulnerable to negative signals.
- Seed Inaccuracy: Seed list testing might not reflect actual inbox placement due to various factors, including ESP and ISP handling.
Key considerations
- Own Domain Links: Ensure all links point to the sender's own domain, not shared EPS domains.
- Volume Increase: Gradually increase sending volume to establish a positive reputation.
- Acquisition Review: Re-evaluate list acquisition methods to ensure high-quality addresses and minimize spam complaints.
- Signal Monitoring: Closely monitor spam complaints, bounces, and engagement metrics.
- Seed List Caution: Interpret seed list results with caution and consider factors not captured by seed testing.
Expert view
Expert from Email Geeks shares a case where a client's emails were going to spam due to links pointing to shared EPS domains. Switching to links pointing to their own domain resolved the issue.
11 Oct 2023 - Email Geeks
Expert view
Expert from Word to the Wise shares that inbox placement rates might differ from seed list results. Email might be delivered to the inbox of seed addresses but still land in the spam folder for real users. It could be due to the content or other factors not captured by seed testing, or ESP might treat seed lists differently.
2 Nov 2023 - Word to the Wise
What the documentation says
4 technical articles
According to documentation from Google, Mailchimp, Microsoft and RFC, even with good open rates and proper authentication (SPF, DKIM, DMARC), emails can still land in the spam folder during subdomain warmup. This is due to factors such as low sender reputation (influenced by user complaints, spam trap hits, and sending practices), poor list hygiene (sending to old, unengaged, or purchased lists), negative IP reputation from previous use, and misconfigured or incomplete authentication protocols. Good open rates do not guarantee inbox placement if overall reputation is poor.
Key findings
- Sender Reputation: Low sender reputation can cause emails to land in spam, even with proper authentication and good open rates.
- List Hygiene: Poor list hygiene, including unengaged or purchased lists, increases spam complaints and harms sender reputation.
- IP Reputation: Negative IP reputation, even on dedicated domains, can impact inbox placement.
- Authentication Issues: Misconfigured or incomplete SPF, DKIM, and DMARC can contribute to spam folder placement.
Key considerations
- Improve Sender Reputation: Focus on improving sender reputation through ethical sending practices, reducing spam complaints, and avoiding spam traps.
- Clean Email Lists: Regularly clean email lists to remove unengaged subscribers and avoid sending to purchased or old lists.
- Monitor IP Reputation: Monitor IP reputation and take steps to improve it if necessary, such as contacting the ESP to resolve any issues.
- Check Authentication: Verify that SPF, DKIM, and DMARC are properly configured and complete, including all sending sources and enforced policies.
Technical article
Documentation from Microsoft says that IP reputation, even on dedicated sending domains, plays a role in deliverability. If the IP address associated with the new subdomain was previously used for spam or has a poor history, it can negatively impact inbox placement despite proper authentication.
26 May 2023 - Microsoft
Technical article
Documentation from Mailchimp explains that poor list hygiene can affect deliverability, even with a new subdomain. Sending to old, unengaged, or purchased lists increases the risk of spam complaints, which harms sender reputation. Regularly cleaning your list and focusing on engaged subscribers will improve inbox placement.
12 Sep 2021 - Mailchimp
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