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Avoiding Spam Filters and Improving Deliverability

Ensure your emails reach inboxes, not spam folders.

How to Improve Email Deliverability: DKIM, SPF, DMARC, and Testing Tips

Email deliverability isn’t just about writing great content—it’s about making sure your messages reach inboxes instead of spam folders. Here’s how to configure domain authentication, test your emails, and avoid common errors that trigger spam filters.

1. Core Domain Authentication Settings

  • DKIM (DomainKeys Identified Mail):
    Adds a digital signature to your emails, verifying that the message was authorized by your domain.
    How to set it up:

    1. Generate a DKIM key in your email provider’s settings.
    2. Add the provided DKIM record to your domain’s DNS settings.
    3. Test and verify using your email platform’s authentication check.

  • SPF (Sender Policy Framework):
    Specifies which mail servers are allowed to send emails on behalf of your domain—helping to prevent spoofing and phishing.
    How to set it up:

    1. Create an SPF TXT record in your DNS:
      Example: v=spf1 include:mailprovider.com ~all
    2. Only include trusted senders in your SPF record.

  • DMARC (Domain-based Message Authentication, Reporting & Conformance):
    Sets a policy for how mail servers should handle unauthorized emails (quarantine, reject, report).
    How to set it up:

    1. Add a DMARC TXT record to your DNS.
      Example for reporting only:
      v=DMARC1; p=none; rua=mailto:your@email.com
    2. Adjust the p (policy) as needed (none, quarantine, or reject).

Tip:
If you’re unsure, contact your domain host or email provider for exact steps and copy-paste-ready DNS records.

2. Testing Deliverability with Diagnostic Tools

  • Mail-Tester (www.mail-tester.com):

    • Send a test email to a unique address provided by Mail-Tester.
    • Get a deliverability score and specific feedback on authentication, spam triggers, and blacklisting.

  • GlockApps (www.glockapps.com):

    • Allows you to test with multiple ISPs (Gmail, Outlook, Yahoo, etc.).
    • Provides reports on inbox/spam placement, authentication pass/fail, and more.

Action:
Use these tools before every major campaign launch to identify technical or content issues that could harm deliverability.

3. Common Red Flags in Copy and Formatting

  • Spammy Language:
    Avoid words like “free,” “guaranteed,” “make money fast,” excessive exclamation marks (!!!), or all CAPS.
  • Bad HTML Coding:
    Don’t copy-paste from Word—this can add messy code. Always use your email platform’s editor and send test emails.
  • Overloading Images:
    Emails with only images or very large images (without sufficient supporting text) often trigger spam filters.
  • Broken or Missing Unsubscribe Links:
    Always include a working unsubscribe option—missing this damages deliverability and violates regulations.

Summary:
Securing your domain with DKIM, SPF, and DMARC, regularly testing send quality, and avoiding common content mistakes are essential to maximizing your email deliverability. Take the time to authenticate, test, and refine both your technical setup and your messaging for every send.

Here’s an expanded, easy-to-read version of your article:

Email Deliverability Essentials: Configuring DKIM, SPF, and DMARC + Testing Your Emails

Improving deliverability means making sure your emails actually land in inboxes—not spam folders. Here’s how to authenticate your sending domain, test your campaigns, and avoid common pitfalls that get legitimate email blocked.

1. Set Up Domain Authentication: DKIM, SPF, and DMARC

  • DKIM (DomainKeys Identified Mail):

    • Digitally signs your emails, verifying they come from your domain and haven’t been tampered with.
    • How to set up:
      1. Obtain DKIM records from your email provider (e.g., HubSpot, Mailchimp, Gmail).
      2. Add them as TXT records in your DNS/hosting control panel.
      3. Verify setup in your provider’s settings.

  • SPF (Sender Policy Framework):

    • Specifies which mail servers are allowed to send on behalf of your domain, blocking fakes and spoofing.
    • How to set up:
      1. Create an SPF TXT record in your DNS. Example: v=spf1 include:mailprovider.com ~all
      2. Edit the record if you add/remove email services.

  • DMARC (Domain-based Message Authentication, Reporting & Conformance):

    • Ties together SPF and DKIM, providing instructions to receiving mail servers about what to do with unauthenticated emails.
    • How to set up:
      1. Add a DMARC TXT record to your DNS. Example: 
        v=DMARC1; p=none; rua=mailto:your@email.com
      2. Review reports and adjust policy (p) from none (just monitor) to quarantine or reject as desired.

Tip:
If you’re not comfortable with DNS changes, your IT provider or domain host can help add these records correctly.

2. Test Your Emails Before You Send

  • Mail-Tester (https://www.mail-tester.com/):

    • Send a draft email to their provided address.
    • Get a detailed score, with advice on missing authentication, spam trigger words, or blacklist issues.

  • GlockApps (https://glockapps.com/):

    • Lets you test with multiple email providers (Gmail, Outlook, Yahoo, etc.).
    • Results show you if your email reaches the primary inbox, the promotions tab, or gets filtered as spam.

Best Practice:
Test every new or changed campaign before you schedule or send a large blast.

3. Avoid Red Flags in Copy and Formatting

  • Spammy Language:
    Phrases like “buy now,” “make millions,” “guaranteed,” or lots of exclamation marks and all caps can get filtered.
  • Poor or Messy HTML:
    Copy-pasting from Word or using malformed HTML in drag-and-drop editors can trigger spam filters.
  • Image-Only Emails:
    Avoid emails that are just images—include plenty of relevant plain text and ALT tags.
  • Missing Unsubscribe/Bad Links:
    Failing to add an easy, working unsubscribe link (or having broken links) is a big deliverability risk.

Summary:
Reliable email delivery takes both technical work (DKIM, SPF, DMARC, and testing) and smart content choices (clean copy and code, real value, easy unsubscribes). Setting this up properly will maximize your chances of reaching every inbox, every time.