How can I improve email deliverability when emails are going to spam?
Matthew Whittaker
Co-founder & CTO, Suped
Published 2 May 2025
Updated 17 Aug 2025
9 min read
Emails going straight to the spam folder can be incredibly frustrating, especially when they prevent important messages from reaching their intended recipients. It impacts not only marketing campaigns but also critical operational communications, as seen when even internal emails start hitting spam filters. The core of this issue often lies with your sender reputation and how your emails are perceived by mailbox providers.
Many factors contribute to this problem, ranging from technical misconfigurations to the very way you acquire and manage your email lists. Understanding these underlying causes is the first step toward effective troubleshooting and improving your email deliverability. It's a complex landscape, but with a structured approach, you can significantly enhance your inbox placement rates and ensure your messages land where they belong.
Understanding sender reputation
Your sender reputation is arguably the most crucial factor determining whether your emails reach the inbox or are diverted to the spam (or junk) folder. This reputation is built over time based on various signals, including your sending volume, bounce rates, spam complaint rates, and engagement metrics like opens and clicks. If recipients frequently mark your emails as spam, or if your bounce rates are high, your reputation will suffer.
A common pitfall that severely damages sender reputation is sending emails to unconsented recipients, such as those scraped from online platforms like LinkedIn. These recipients have not opted in to receive your communications, leading to high complaint rates and low engagement, which signals to mailbox providers that your emails are unwelcome. This practice can quickly trash your domain reputation, making it difficult for even legitimate emails to get through. It's a key reason why many organizations struggle with email deliverability, especially in B2B contexts where unsolicited outreach is common.
Beyond explicit spam complaints, low engagement also harms your standing. If your emails are consistently ignored, deleted without being opened, or lead to unsubscribes, it indicates to mailbox providers that your content isn't relevant or desired. This can subtly degrade your reputation over time. You can learn more about how to improve your overall sender reputation and deliverability by exploring our guide on improving your email and domain reputation.
Strengthening email authentication
Email authentication protocols like Sender Policy Framework (SPF), DomainKeys Identified Mail (DKIM), and Domain-based Message Authentication, Reporting, and Conformance (DMARC) are fundamental to proving your emails are legitimate and not spoofed. These records tell recipient servers that an email purportedly from your domain is indeed authorized by you. Without them, your emails are much more likely to be flagged as suspicious or spam.
A common scenario involves a DMARC record being added without fully understanding its implications. While setting up DMARC is critical for email security and deliverability, an improperly configured DMARC policy can lead to legitimate emails being quarantined or rejected. For instance, if your DMARC record is set to a p=reject policy without proper SPF and DKIM alignment, authorized emails could fail authentication checks. We have a detailed guide on DMARC, SPF, and DKIM that can help.
Furthermore, issues with PTR records (Pointer Records), while less common as a direct cause of spam filtering for domains using major email service providers like Google or Mailgun, can still contribute to a weaker overall authentication posture. These records help confirm that the IP address sending the email corresponds to the sending domain. While Gmail handles its own IP addresses and PTR records, any custom configurations or third-party sending via platforms like Marketo or Outreach should have their DNS settings verified to ensure everything is correctly aligned and authenticated.
DMARC implementation
Ensure your DMARC policy is implemented gradually, starting with a p=none setting to monitor reports before moving to quarantine or reject policies. This allows you to identify and fix any authentication issues without impacting your legitimate email flow.
Content, engagement, and sending practices
The content of your emails plays a significant role in deliverability. Overly promotional language, excessive use of all caps, too many images without text, or embedded links to suspicious domains can trigger spam filters. Focus on creating valuable, engaging content that your audience genuinely wants to receive. Personalization and relevance are key to encouraging opens and clicks, which in turn boosts your sender reputation.
Engagement is a two-way street. Mailbox providers closely observe how recipients interact with your emails. High open rates, click-through rates, and low unsubscribe rates signal positive engagement, indicating your emails are desired. Conversely, low engagement can lead to your emails being filtered. Encouraging recipients to reply, add you to their address book, or click on links can significantly improve your deliverability. Learn more about increasing your email click through rate.
Consistency in your sending volume and frequency also helps establish a predictable sending pattern. Sudden spikes in email volume can be perceived as suspicious by spam filters. Gradually warm up new IPs or domains if you plan to send large volumes. For a comprehensive overview of best practices, you can refer to HubSpot's guide on email deliverability.
Poor practices
Unverified lists: Sending to email addresses obtained through scraping or purchased lists without explicit consent.
Infrequent cleaning: Not removing inactive subscribers, bounced addresses, or spam traps regularly.
Single opt-in: Allowing subscribers to join your list without confirming their email address, leading to invalid or spam trap addresses.
Best practices
Permission-based: Only send to recipients who have explicitly opted in, preferably through a double opt-in process.
Regular hygiene: Implement a robust process to clean your email lists regularly, removing inactive or invalid addresses.
Double opt-in: Use double opt-in to verify new subscribers, ensuring high-quality and engaged contacts.
List hygiene and monitoring
Maintaining a clean and engaged email list is paramount. Spam traps, which are email addresses used to identify spammers, can severely damage your sender reputation if you send to them. Regularly validating and cleaning your email list to remove inactive or invalid addresses helps avoid these traps and reduces bounce rates. This is one of the most effective strategies for long-term deliverability success.
Monitoring your domain and IP reputation is crucial for identifying deliverability issues early. Tools like Google Postmaster Tools provide valuable insights into your sending reputation with Gmail and other major mailbox providers. They can show you your spam rate, IP reputation, and domain reputation, helping you pinpoint specific problems.
Additionally, regularly checking if your domain or IP address is listed on any email blacklists (also known as blocklists) is essential. Being on a blacklist can immediately send your emails to spam or block them entirely. While some blocklists are less impactful than others, presence on major ones can significantly hinder your deliverability. Our guide on email blacklists can provide more information on this topic.
The perception that problematic PTR records are the primary cause of emails going to spam is a common misconception, especially when using email service providers that manage their own IP infrastructure, such as Gmail or Outreach. These providers handle the reverse DNS setup, making PTR issues on your end unlikely to be the root cause. Instead, focus on the more impactful areas like sender reputation, authentication, and list hygiene.
Additional deliverability considerations
Sometimes, the simplest solutions can make a big difference. For example, asking recipients to whitelist your email address or domain can help ensure your emails always land in their inbox. This is especially useful for important, one-to-one communications or critical transactional emails. Additionally, complying with anti-spam regulations (like CAN-SPAM or GDPR) is not just a legal requirement but also a fundamental best practice for good deliverability.
Regularly testing your email deliverability can give you a clearer picture of where your emails are landing. Many tools allow you to send test emails to various mailbox providers to see if they reach the inbox, spam folder, or are blocked entirely. This allows for proactive identification and resolution of issues. For more best practices on avoiding spam filters, review our article on email deliverability best practices.
Finally, understanding the nuances of how different mailbox providers operate can be beneficial. For instance, Yahoo and Microsoft (Outlook, Hotmail) have specific requirements, especially regarding bulk senders, which include strong authentication (SPF, DKIM, DMARC), low spam rates, and easy unsubscribe options. Adhering to these requirements is crucial for consistent inbox placement. More details are available in this Mailgun article on avoiding spam.
Views from the trenches
Best practices
Always prioritize permission-based email acquisition; obtain explicit consent from recipients before sending.
Implement double opt-in for all new subscribers to verify their email addresses and genuine interest.
Regularly clean your email lists by removing inactive, unengaged, or bounced addresses to improve quality.
Monitor your sender reputation using tools like Google Postmaster Tools and address any negative trends proactively.
Ensure SPF, DKIM, and DMARC authentication records are correctly configured for all sending domains.
Common pitfalls
Sending emails to lists acquired without consent, such as scraped or purchased contacts, leads to high spam complaints.
Neglecting email list hygiene, allowing old, invalid, or spam trap addresses to remain on your active lists.
Improperly configuring DMARC, SPF, or DKIM records, which can cause legitimate emails to fail authentication.
Focusing solely on technical aspects while overlooking content quality and recipient engagement metrics.
Sudden, large spikes in email sending volume without prior IP or domain warming can trigger spam filters.
Expert tips
Understand that enterprise spam filters are often less forgiving than consumer ones for B2B unsolicited email.
Use email deliverability testing tools to simulate inbox placement across various mailbox providers.
Consider segmenting your audience and tailoring content to different segments to increase relevance and engagement.
Encourage recipients to whitelist your email address or add you to their contacts for critical communications.
Continuously adapt to evolving mailbox provider policies, as rules for bulk senders are frequently updated.
Marketer view
Marketer from Email Geeks says the primary reason emails are marked as spam is a lack of recipient permission. Focusing on proper email acquisition is essential. Incorrect PTR records are not typically the cause, and incorrect DMARC implementation can worsen deliverability.
2023-10-10 - Email Geeks
Marketer view
Marketer from Email Geeks says understanding your email setup is vital, including where emails are sent from, the type of content, and the target audience.
2023-10-10 - Email Geeks
Achieving inbox success
Improving email deliverability when emails are going to spam requires a multi-faceted approach, focusing on foundational elements like sender reputation, email authentication, content quality, and disciplined list management. While technical configurations such as DMARC are crucial, they must be implemented correctly and complemented by strong ethical sending practices. By prioritizing permission, nurturing engagement, and continuously monitoring your performance, you can significantly increase your chances of reaching the inbox and maintaining a healthy email program.
Google or 
Mailgun, can still contribute to a weaker overall authentication posture. These records help confirm that the IP address sending the email corresponds to the sending domain. While Gmail handles its own IP addresses and PTR records, any custom configurations or third-party sending via platforms like Marketo or Outreach should have their DNS settings verified to ensure everything is correctly aligned and authenticated.
Outreach. These providers handle the reverse DNS setup, making PTR issues on your end unlikely to be the root cause. Instead, focus on the more impactful areas like sender reputation, authentication, and list hygiene.
Yahoo and 
Microsoft (Outlook, Hotmail) have specific requirements, especially regarding bulk senders, which include strong authentication (SPF, DKIM, DMARC), low spam rates, and easy unsubscribe options. Adhering to these requirements is crucial for consistent inbox placement. More details are available in this Mailgun article on avoiding spam.
