How to improve email deliverability after sending cold emails and having low domain reputation?
Matthew Whittaker
Co-founder & CTO, Suped
Published 14 Aug 2025
Updated 17 Aug 2025
7 min read
Finding your legitimate emails landing in the spam folder after a period of cold outreach can be frustrating. You might have noticed your domain reputation plummeting in tools like Google Postmaster Tools, leaving you wondering how to recover. This is a common challenge, as mailbox providers closely scrutinize sending behavior, and even a small volume of problematic emails can have a significant impact on your sender score.
The good news is that a damaged domain reputation is not permanent. It requires a strategic and patient approach to rebuild trust with internet service providers (ISPs) and get your messages back into the inbox. This guide will walk you through the necessary steps to improve your email deliverability and restore your domain's health.
The root cause of reputation damage
Cold outreach, by its nature, often involves sending emails to recipients who haven't explicitly opted in to receive communications. This significantly increases the likelihood of negative engagement, such as recipients marking your emails as spam, deleting them without opening, or high bounce rates from unverified addresses. These actions signal to ISPs that your sending practices are undesirable, leading to a rapid decline in your domain's reputation.
ISPs like Gmail use sophisticated algorithms to evaluate a sender's reputation based on various factors, including complaint rates, bounce rates, and engagement metrics. When these metrics fall below acceptable thresholds, your emails are more likely to be diverted to the spam folder or blocked entirely. Even a small number of spam complaints can severely impact your domain's sending ability.
Understanding how your domain reputation is being perceived is the first step. Tools like Google Postmaster Tools provide valuable insights into your domain's health, including its spam rate and reputation status. Addressing a bad domain reputation is crucial to improving deliverability.
Foundation for recovery: Technical health
Even if your email authentication protocols, such as SPF, DKIM, and DMARC, are currently passing, it's vital to ensure they are correctly implemented and maintained. These protocols act as digital signatures, verifying that your emails are legitimate and haven't been tampered with in transit. Proper configuration helps ISPs trust your sending domain.
For example, while the EHLO domain not matching the PTR record is a common observation, particularly with providers like Microsoft Office 365, this specific mismatch generally does not impact deliverability. ISPs primarily rely on SPF, DKIM, and DMARC for sender authentication, so focusing on these is more critical. You can learn more about these protocols in this simple guide.
Review your DMARC policy. While a p=none policy allows emails to be delivered even if they fail DMARC, it's a starting point. Once you have a clear understanding of your email flow, aim to move to a stricter policy like p=quarantine or p=reject to enforce stricter protection against spoofing and unauthorized sending.
Using a reputable email service provider (ESP) for your legitimate marketing or transactional emails is also critical. They often manage dedicated IP addresses and have systems in place to ensure good sending practices across their user base, which indirectly benefits your deliverability. If you've been using a less specialized service, consider migrating your main sending volume.
Strategic sending practices
After a period of low reputation, you must undertake a domain warm-up process. This involves gradually increasing your sending volume with highly engaged recipients. Start with small, highly relevant batches of emails to your most active subscribers. This consistent, positive sending behavior helps rebuild trust with ISPs over time, signaling that you are a legitimate sender.
One of the quickest ways to improve your deliverability is through rigorous list hygiene. Regularly clean your email lists to remove inactive, invalid, or bouncing addresses. Sending to unengaged or non-existent recipients not only wastes resources but also severely damages your sender reputation by increasing bounce rates and potentially hitting spam traps. A clean list ensures you're only sending to recipients who are likely to engage positively.
Focus on crafting relevant and valuable content. Personalization goes beyond just using a recipient's name, it means tailoring your message to their specific needs and interests. Highly engaged recipients are less likely to mark emails as spam, and positive interactions like opens, clicks, and replies send strong positive signals to ISPs. This focus on content is key to getting your emails delivered to the inbox.
Previous cold email approach
Unverified lists: Sending to unverified or purchased email addresses.
High volume: Rapidly sending a large number of emails from a new or cold domain.
Generic content: Using standardized, impersonal email templates.
Ignoring metrics: Not monitoring bounce rates or spam complaints.
New strategic approach
Verified lists: Sending only to clean, verified, and opted-in email addresses. According to EmailToolTester, this is a key best practice.
Gradual warm-up: Slowly increasing volume to build sender trust.
Personalized content: Crafting unique and highly relevant messages for recipients.
Active monitoring: Continuously tracking key metrics and adjusting strategy.
Monitoring and long-term maintenance
Once you've implemented the technical fixes and started rebuilding your sender reputation through strategic sending, continuous monitoring becomes paramount. This involves regularly checking for any signs of continued issues, such as your domain being placed on an email blocklist (or blacklist).
Being on a blacklist (or blocklist) can severely impede your deliverability. If your domain or IP address ends up on a major blocklist, ISPs will likely reject your emails outright. Understanding what happens when your domain is blocklisted is critical. Regular checks and prompt action to delist, if necessary, are part of maintaining a healthy sender reputation. An in-depth guide to email blocklists can provide further insight.
Keep a close eye on your key email metrics. High bounce rates, low open rates, and increased complaint rates are all indicators that your deliverability is still suffering. Adjust your sending volume and content based on these metrics. Consistency and patience are key, as rebuilding trust with ISPs takes time and sustained positive behavior. This proactive approach will help you to resolve deliverability issues.
Metric
Good range
Action if poor
Complaint rate
< 0.1%
Improve content relevance, make unsubscribe easy
Bounce rate
< 2%
Clean your email list, verify addresses
Engagement rate
Higher is better
Segment audience, personalize messages
Proactive steps for long-term success
Maintaining a strong domain reputation is an ongoing effort. It's not a one-time fix but a continuous commitment to best practices. Focus on building genuine relationships with your audience and consistently providing value. This approach will lead to better inbox placement and overall email program success.
Restoring trust and deliverability
Recovering your email deliverability and domain reputation after cold emailing is a journey that demands discipline and adherence to best practices. By addressing technical configurations, carefully warming up your domain, rigorously cleaning your lists, and consistently sending valuable content, you can gradually restore trust with ISPs.
Remember that patience is vital. Reputation recovery can take weeks or even months, depending on the severity of the initial damage and the consistency of your efforts. By committing to these practices, you'll not only improve your inbox placement but also build a healthier, more sustainable email marketing program for the future.
Views from the trenches
Best practices
Always maintain a clean, verified email list to minimize bounces and spam trap hits.
Implement a gradual domain warm-up process after any reputation issues, increasing volume slowly.
Focus on sending highly relevant and engaging content to your recipients to encourage positive interactions.
Regularly monitor your domain's health using tools like Google Postmaster Tools and blocklist checkers.
Common pitfalls
Sending cold emails from your primary domain, which can quickly damage its reputation.
Ignoring high complaint rates or bounce rates, which are critical indicators of deliverability issues.
Expecting instant recovery of domain reputation; it is a time-consuming process.
Not configuring SPF, DKIM, and DMARC correctly, even if they appear to be passing.
Expert tips
Consider using a secondary domain for any cold outreach campaigns to protect your main domain's reputation.
Make it easy for recipients to unsubscribe, as this is preferable to them marking your emails as spam.
Consistently analyze engagement metrics, not just delivery rates, to understand recipient behavior.
For Microsoft Office 365, EHLO domain not matching the PTR record is normal and does not affect deliverability.
Expert view
Expert from Email Geeks says that Microsoft's infrastructure has never matched the EHLO domain with the PTR record, and this behavior does not impact email deliverability.
2024-04-17 - Email Geeks
Expert view
Expert from Email Geeks says that cold emails are inherently considered spam, and this is typically the primary reason for deliverability problems. An 11% complaint rate is extremely high, as guidelines suggest staying under 0.03%.
Gmail use sophisticated algorithms to evaluate a sender's reputation based on various factors, including complaint rates, bounce rates, and engagement metrics. When these metrics fall below acceptable thresholds, your emails are more likely to be diverted to the spam folder or blocked entirely. Even a small number of spam complaints can severely impact your domain's sending ability.
Microsoft Office 365, this specific mismatch generally does not impact deliverability. ISPs primarily rely on SPF, DKIM, and DMARC for sender authentication, so focusing on these is more critical. You can learn more about these protocols in this simple guide.
