Email deliverability is the percentage of your sent emails that land in the recipient's primary inbox. To fix it, you must verify your domain authentication, clean your subscriber list, and monitor your sender reputation. This guide walks you through the exact technical settings and list hygiene practices required to get your messages out of spam folders and into the inbox.
Why is my email deliverability bad?
You are likely asking this because your open rates have dropped, your bounce rate has spiked, or you are receiving complaints that your messages are going to spam. The cause is almost always one of three things: missing or broken authentication records, a dirty email list, or a damaged sender reputation. Mailbox providers like Gmail, Yahoo, and Outlook use algorithms to decide where your email lands. If your domain fails their trust checks, or if your sending pattern looks like a spammer, they filter your messages. You cannot fix what you cannot measure. You need to identify which of these three areas is failing before you make changes.
Check your authentication records
Authentication is the foundation of trust. Without it, your emails fail basic security checks before they even reach the spam filter. You need three specific DNS records: SPF, DKIM, and DMARC.
SPF stands for Sender Policy Framework. It is a DNS TXT record that lists which mail servers are authorized to send email on behalf of your domain. If a server sends an email from your domain but is not listed in your SPF record, the receiving server flags it as suspicious.
DKIM stands for DomainKeys Identified Mail. It adds a digital signature to your outgoing emails. This signature proves that the message has not been altered in transit and that it truly came from your domain.
DMARC stands for Domain-based Message Authentication, Reporting, and Conformance. It tells receiving servers what to do when an email fails SPF or DKIM checks. It also sends you reports on who is sending email from your domain, which helps you find unauthorized senders.
To fix this, log into your domain registrar or DNS provider. Look for the TXT records. Ensure your SPF record includes all your sending services, such as your CRM, marketing automation tool, and transactional email provider. If you have multiple services, combine them into one SPF record using include statements. Do not create multiple SPF records, as this causes a syntax error and breaks authentication.
Next, enable DKIM signing in your email service provider. Most platforms, like Mailchimp, HubSpot, or Brevo, have a setting to generate a DKIM key. Copy that key into your DNS records. Once both SPF and DKIM are active, set up DMARC. Start with a policy of p=none. This tells servers to only report failures without blocking email. After a few weeks, review the reports. If you see no unauthorized senders, change the policy to p=quarantine. This moves failing emails to spam. Finally, once you are confident, set it to p=reject. This blocks failing emails entirely. You can verify your records are working by using a tool like MXToolbox to check your DNS configuration.
Clean your email list
A dirty list is the second biggest killer of deliverability. If you send emails to addresses that do not exist, the server sends a hard bounce. If a large percentage of your emails hard bounce, mailbox providers assume you are buying lists or scraping data. This damages your sender reputation.
You need to keep your bounce rate below 2%. Below 0.5% is excellent. Between 0.5% and 2% is acceptable. Above 2% is dangerous. Above 5%, many email service providers will pause or suspend your account.
To clean your list, start by removing hard bounces immediately. These are permanent failures where the email address does not exist. Never retry these. For soft bounces, which are temporary issues like a full mailbox, retry two or three times. If the address keeps bouncing, suppress it.
Next, look for inactive subscribers. If someone has not opened an email in six months, they are a liability. They are not engaging with your content, which lowers your engagement metrics. Worse, they might be a spam trap. A spam trap is an email address that exists only to catch spammers. If you hit a spam trap, your reputation takes a severe hit. Remove or segment inactive users. You can try a re-engagement campaign. Send a simple email asking if they still want to receive updates. If they do not open or click, remove them from your list.
Use a double opt-in process for new sign-ups. This means the user confirms their email address by clicking a link in a verification email. This ensures the address is valid and that the person actually wants to hear from you. It prevents typos and fake addresses from entering your list.
Monitor your sender reputation
Your sender reputation is your track record with mailbox providers. It works like a credit score. High bounce rates, spam complaints, and low engagement lower your score. A low score means your emails go to spam.
You can check your reputation using Google Postmaster Tools. This is a free tool from Google that shows you your domain and IP reputation. It also shows you the percentage of your emails landing in spam. If you see a drop in reputation, investigate immediately. Look for recent changes. Did you start a new campaign? Did your bounce rate spike? Did you receive a spike in spam complaints?
Spam complaints are the most damaging metric. One complaint per 1,000 emails is usually acceptable. If you see complaints from a specific campaign or segment, stop sending to that segment. Remove complainers from your list immediately. Do not try to win them back. They have told you your email is unwanted. Respecting that is the only way to protect your reputation.
Use a dedicated IP address for high-volume sending. If you share an IP with other senders, their bad behavior can hurt your reputation. A dedicated IP isolates your sending history. However, a new IP has no reputation. You must warm it up.
Warm up new domains and IPs
If you are starting with a new domain or a new IP address, you have no history. Mailbox providers do not know you. If you send 5,000 emails on day one, you will be flagged as a spammer. You must warm up your sending gradually.
A typical warm-up schedule takes four to eight weeks.
- Weeks 1 to 2: Send 25 to 50 emails per day. Send only to your most engaged contacts. These are people who open and click your emails regularly.
- Weeks 3 to 4: Increase to 100 to 500 emails per day. Continue to prioritize engaged contacts.
- Weeks 5 to 6: Increase to 1,000 to 5,000 emails per day. You can start including less engaged contacts.
- Weeks 7 to 8: Increase to 10,000 to 50,000 emails per day. At this point, you can send to your full list.
During warm-up, monitor your metrics daily. Watch your open rates, click-through rates, and bounce rates. If your bounce rate spikes, slow down. If your spam complaints increase, stop and investigate. High engagement during warm-up signals to inbox providers that recipients want your mail. This builds your reputation positively.
Optimize your email content
Content quality affects how spam filters treat your messages. Spam filters look for patterns that resemble spam. You need to avoid these patterns.
Avoid spam trigger words. Words like "free," "urgent," "act now," and "buy now" are common in spam. Using them heavily can flag your email. Use them sparingly or not at all.
Keep your email text-based. Heavy use of images, HTML, and links can trigger filters. A simple, text-heavy email with clear formatting is often safer. If you use images, ensure they have alt text. Do not hide text inside images.
Ensure your unsubscribe link is visible and functional. It should be in the footer, clearly labeled, and work with one click. If a user has to dig through multiple pages to unsubscribe, they are more likely to mark your email as spam instead.
Personalize your subject lines and body text. Generic, mass-produced content looks like spam. Use merge tags to insert the recipient's name. Reference their past behavior or interests. This increases engagement and signals to the provider that the content is relevant.
Test and monitor continuously
Deliverability is not a one-time fix. It is an ongoing process. You need to test your emails before you send them to your full list.
Use a testing tool to check your spam score. Tools like Mail-Tester or GlockApps analyze your email for authentication errors, content issues, and spam triggers. They give you a score out of 10. Aim for a score above 8.
Run inbox placement tests. This involves sending your email to real inboxes of Gmail, Outlook, and Yahoo accounts. You can use a service like 250ok to do this. This tells you exactly where your email lands. If it lands in promotions or social tabs in Gmail, that is still a form of filtering. You want it in the primary inbox.
Monitor your metrics regularly. Check your bounce rate, open rate, and complaint rate weekly. If you see a trend, investigate it. A sudden drop in open rates might mean your domain reputation dropped. A spike in bounces might mean your list is dirty.
If you are struggling to get your emails into the inbox, or if you are sending cold emails and seeing low response rates, consider getting help. We can set up your cold email infrastructure to ensure your domain is authenticated, your IP is warmed up, and your sending practices are compliant. This saves you time and protects your reputation.
For more on how to structure your email campaigns for maximum engagement, read our guide on email marketing best practices. If you are using a CRM, check our article on integrating your CRM with email tools to ensure your data is clean and synced.
Summary of key actions
To fix email deliverability, follow these steps in order:
- Verify authentication: Ensure SPF, DKIM, and DMARC records are correct. Start DMARC at p=none, then move to p=reject.
- Clean your list: Remove hard bounces and inactive subscribers. Use double opt-in for new sign-ups.
- Check reputation: Use Google Postmaster Tools to monitor your domain reputation. Investigate any drops immediately.
- Warm up new IPs: Increase sending volume gradually over four to eight weeks. Prioritize engaged contacts.
- Optimize content: Avoid spam trigger words. Keep emails text-based. Ensure unsubscribe links work.
- Test before sending: Use tools like Mail-Tester to check your spam score. Run inbox placement tests.
By following these steps, you build a foundation of trust with mailbox providers. Your emails will land in the inbox, not the spam folder. This leads to higher open rates, more clicks, and better results from your campaigns.
If you need help with any of these steps, or if you want to build a robust email system from scratch, contact us for a consultation. We can audit your current setup and identify the specific issues affecting your deliverability.