This guide walks you through a complete email deliverability audit in roughly two to three hours. By the end, you will know exactly why your emails are missing the inbox, and you will have a repeatable workflow to fix it and keep it fixed.

What You'll Build

  • A documented audit checklist covering DNS authentication, sender reputation, list hygiene, and content scoring
  • A working SPF, DKIM, and DMARC configuration verified against live DNS records
  • A reusable Notion or Google Sheets template to run this audit quarterly
  • A baseline deliverability score you can track over time using free and paid tools
  • A prioritised fix list so you tackle the highest-impact issues first

Prerequisites

  • Access to your domain's DNS records (via your registrar or Cloudflare, Route 53, etc.)
  • Admin access to your email sending platform (Klaviyo, HubSpot, Loops, Mailchimp, or similar)
  • A sending domain you own (not a free Gmail or Outlook address)
  • A free account on MXToolbox and Mail-Tester
  • Optional: access to Google Postmaster Tools if you send to Gmail addresses at volume

Step 1: Check Your DNS Authentication Records

Authentication is the foundation of deliverability. Gmail, Outlook, and Yahoo all check SPF, DKIM, and DMARC before deciding where to place your email. As of 2026, Google and Yahoo enforce DMARC as a hard requirement for bulk senders sending more than 5,000 messages per day.

How do you check SPF?

Go to MXToolbox and run an SPF lookup against your sending domain. A passing SPF record looks like this:

v=spf1 include:sendgrid.net include:klaviyo.com ~all

Each include: entry should match an authorised sending service. The ~all softfail is safer than ?all but weaker than -all. Move to -all once you have confirmed all sending sources are listed.

Common pitfall: SPF has a 10 DNS lookup limit. If you use multiple sending tools, you can exceed this limit silently. Use dmarcian's SPF flattener to count and compress your lookups.

How do you verify DKIM?

Find the DKIM selector your sending platform provides. In Klaviyo, for example, it is usually klaviyo1._domainkey.yourdomain.com. Run a DKIM lookup in MXToolbox using that selector. You should see a valid public key in the TXT record.

If your platform has not published a CNAME for DKIM yet, do that now. Most platforms have a step-by-step guide inside their DNS settings screen.

How do you set up DMARC if you do not have one?

Add a TXT record at _dmarc.yourdomain.com. Start with a monitoring policy so you do not block legitimate mail while you audit:

v=DMARC1; p=none; rua=mailto:[email protected]; ruf=mailto:[email protected]; fo=1;

The rua address receives aggregate XML reports daily. Use a service like dmarcian or Postmark's DMARC tool to parse those reports into readable dashboards. After two weeks of clean data, move the policy to p=quarantine, then eventually p=reject.

Step 2: Score Your Current Deliverability Baseline

Before fixing anything else, capture a baseline score. This gives you a before-and-after comparison and helps you prioritise fixes.

Send a test email to the address provided by Mail-Tester. After it arrives, visit your Mail-Tester results page. The tool scores your email out of 10 and breaks down issues across authentication, content, blacklist status, and server configuration. A score of 8 or below warrants immediate attention. Most healthy senders land between 9 and 10.

Record your score in your audit template alongside the date, the sending domain, and the sending platform. You will repeat this after each fix to measure improvement.

Step 3: Audit Your Sender Reputation

What does sender reputation actually measure?

Internet service providers (ISPs) assign a reputation score to your sending IP address and domain. This score is based on complaint rates, bounce rates, spam trap hits, and engagement history. A damaged reputation can land you in spam even if your authentication is perfect.

How do you check IP and domain reputation?

Run your sending IP through these tools:

If your sending IP is on a blocklist, follow the delisting instructions on each registry. Most delisting requests are approved within 24 to 48 hours if you can demonstrate you have fixed the underlying issue.

If you use a shared IP via your ESP (common with Mailchimp and HubSpot starter plans), consider upgrading to a dedicated IP. This isolates your reputation from other senders on the same platform.

Step 4: Clean Your Email List

A dirty list is the single fastest way to tank deliverability. High bounce rates and spam complaints signal to ISPs that you are not maintaining your list responsibly.

What bounce rate is acceptable?

Keep hard bounces below 0.5% per send. Gmail and Yahoo will throttle or block senders who consistently exceed 2%. Most ESPs will suspend your account automatically around that threshold.

Export your list and run it through a verification tool. ZeroBounce and NeverBounce both offer pay-per-verification pricing, typically around $0.003 to $0.008 per email as of mid-2026. For a list of 10,000 contacts, expect to spend $30 to $80 to clean it.

Remove all hard bounces, spam complaints, and addresses marked as invalid immediately. Flag catch-all addresses for a re-engagement campaign before mailing them at full volume.

When should you suppress inactive contacts?

Contacts who have not opened or clicked in the last 90 to 180 days drag down your engagement metrics. ISPs track the ratio of engaged recipients to total recipients. Suppress inactive contacts into a separate segment. Run a short re-engagement sequence of two to three emails with a strong subject line. Anyone who does not respond should be removed from your active list.

This is also a good moment to review your content strategy. If a large portion of your list is inactive, the issue may be content relevance rather than deliverability alone. If you are planning a content refresh, the Lenka Studio social media toolkit has a free content calendar template that can help you plan more consistent, relevant sends across channels.

Step 5: Audit Your Email Content for Spam Signals

Even with perfect authentication and a clean list, certain content patterns will trigger spam filters. Modern filters use machine learning, not just keyword matching, but old-school red flags still apply.

What content signals hurt deliverability?

  • Emails that are all-image with no text. Aim for a text-to-image ratio of at least 60:40.
  • Shortened URLs from services like bit.ly. Use your own domain for tracking links.
  • Subject lines in ALL CAPS or with excessive punctuation (!!!)
  • HTML with broken tags, excessive inline CSS, or tables inside tables
  • Missing or broken unsubscribe links. This is a legal requirement under CAN-SPAM in the US, CASL in Canada, and GDPR in regions affecting Australian and Singaporean senders with EU contacts.

Run your email content through Postmark's Spam Check tool. It scores your content against SpamAssassin rules and flags specific issues with line references.

Step 6: Check Your Sending Infrastructure Settings

What infrastructure settings affect inbox placement?

Make sure your sending domain has a matching reverse DNS (PTR) record. Your ESP usually handles this for shared infrastructure, but on a dedicated IP, you may need to set it manually via your cloud provider (AWS SES, Postmark, SendGrid, etc.).

Confirm that your From address, Reply-To address, and sending domain are all on the same root domain. Mismatches between these reduce trust signals.

If you use Google Postmaster Tools, connect your sending domain and monitor the Domain Reputation and Spam Rate dashboards. Google provides a spam rate threshold of 0.10% for good standing and flags anything above 0.30% as a violation. Check this weekly.

Step 7: Document and Prioritise Your Findings

Pull everything you have found into a single audit document. A simple table works well. Columns for issue, severity (critical, medium, low), fix required, owner, and status.

Prioritise in this order:

  1. Missing or broken DMARC record (critical)
  2. Active blacklist listings (critical)
  3. Hard bounce rate above 0.5% (critical)
  4. Spam complaint rate above 0.10% (critical)
  5. DKIM not publishing correctly (high)
  6. SPF exceeding 10 DNS lookups (high)
  7. Inactive contacts dragging down engagement (medium)
  8. Content spam signals (medium)
  9. Missing PTR record on dedicated IP (low to medium)

Set a review date 30 days out. Run Mail-Tester again after each critical fix to confirm improvement. Repeat the full audit quarterly. If your business is growing its email list quickly, monthly audits are worth the time investment.

At Lenka Studio, we recommend pairing a deliverability audit with a broader brand health review. You can get a fast read on how your brand is performing across channels using the free brand health score assessment.

Frequently Asked Questions

How long does it take to fix a damaged sender reputation?

Reputation recovery typically takes four to eight weeks of consistent, low-volume sending to engaged subscribers. Sending smaller, more targeted batches during this period helps rebuild trust with ISPs faster than blasting your full list.

Does this audit work for transactional emails too?

Yes. The DNS authentication steps and reputation checks apply to all email types. Transactional emails (receipts, password resets) should use a separate subdomain like mail.yourdomain.com so a marketing deliverability issue does not block critical transactional messages.

What if my ESP does not support DKIM on a custom domain?

Switch providers. Every reputable ESP as of 2026 supports custom DKIM signing. If your current provider does not, that limitation alone is a strong reason to migrate to SendGrid, Postmark, Resend, or Loops.

How often should I run a deliverability audit?

Run a full audit quarterly. Run a quick check (Mail-Tester score and bounce rate review) monthly. Monitor Google Postmaster Tools weekly if you send more than 1,000 emails per day.

Will a higher sending volume hurt my deliverability?

Volume alone does not hurt deliverability, but sudden spikes do. ISPs look for irregular patterns. If you plan a large send after a period of low activity, warm up gradually. Increase volume by 20 to 30 percent per day over one to two weeks before hitting your full list.

Next Steps

Work through the audit checklist in the order above. Start with the critical authentication fixes since those have the highest impact on inbox placement. Then clean your list, score your content, and document everything so your next quarterly review takes an hour instead of three.

If you want help building a reliable email marketing system alongside a broader digital strategy, the team at Lenka Studio works with SMBs across Australia, Singapore, Canada, and the US to build workflows that perform consistently. Get in touch to talk through your setup.