Why Your Business Emails Bounce — and How to Fix It

By Veronica Jeans, Ecommerce Expert

Estimated reading time: 6–7 minutes

Email is still one of your most powerful marketing and communication tools—but when your messages suddenly start bouncing or disappearing into spam, it can cause panic. If you’ve ever seen a “550 5.7.26 Unauthenticated email” error, you’ve run headfirst into a domain authentication issue. Let’s break down what’s happening, why it matters, and how to fix it—so your store never loses a sale because of a failed email.

1. What’s Actually Happening When Emails Bounce

When your customers’ inboxes reject your messages, it’s often because your domain isn’t “authenticated.” Email providers like Gmail and Outlook now verify that every email truly comes from the domain it claims to. This verification depends on three behind-the-scenes settings in your DNS:

• SPF (Sender Policy Framework) — lists which servers are allowed to send emails for your domain.
• DKIM (DomainKeys Identified Mail) — digitally signs your outgoing mail to prove it hasn’t been tampered with.
• DMARC (Domain-based Message Authentication, Reporting & Conformance) — enforces that at least one of those checks passes.

If these aren’t set up—or they’re missing a key provider like Google Workspace or Omnisend—your messages fail authentication and bounce back with errors like “550 5.7.26 Unauthenticated email.”

2. Why This Matters for Your Ecommerce Business

In ecommerce, your entire customer experience depends on communication: order confirmations, abandoned cart reminders, shipping updates, and marketing campaigns. If your emails aren’t being delivered, customers lose trust fast—and that directly affects sales.

Beyond the short-term pain, failed authentication damages your domain’s sender reputation. Once email providers flag you as “unverified,” even legitimate messages start landing in spam folders. Recovering from that can take weeks or months.

3. How to Fix the Problem (Step-by-Step)

Here’s how I recommend fixing this quickly and properly:

1. Log in to your DNS provider (GoDaddy, Cloudflare, Shopify, etc.).
2. Check your SPF record. It should include all your sending sources—Google Workspace, Mailgun, Omnisend, Klaviyo, etc. Example:
   v=spf1 include:_spf.google.com include:mailgun.org ~all
3. Verify DKIM. In your email platform (like Google Admin or Omnisend), generate and publish DKIM records. This proves your emails are authentic.
4. Confirm your DMARC policy. Start with a relaxed policy:
   v=DMARC1; p=none; rua=mailto:yourname@yourdomain.com;
   Once everything passes, change it to p=reject to protect your brand.
5. Test your setup. Use tools like mail-tester.com or MXToolbox to confirm SPF, DKIM, and DMARC all pass.

4. Common Mistakes I See Store Owners Make

• Multiple SPF records. You can only have one SPF record—combine all senders into one line.
• Forgetting to add Google or Shopify. Even if you use Omnisend or Klaviyo, you still need to include your primary email platform.
• Skipping DKIM verification. Adding the record isn’t enough—you must activate DKIM in your admin panel.
• Too-aggressive DMARC settings. Setting p=reject too early can cause legitimate emails to bounce. Always test first.

5. Best Practices to Keep Your Email Reputation Strong

• Authenticate early. Set up SPF, DKIM, and DMARC before sending any bulk email campaigns.
• Use one sending domain. Keep marketing and transactional emails under the same authenticated domain for consistency.
• Monitor reports. DMARC reports show who’s sending on your behalf—review them monthly to spot unauthorized use.
• Stay under SPF lookup limits. SPF allows a maximum of 10 lookups. Simplify includes where possible.
• Check regularly. Anytime you add a new platform or app that sends email, update your records.

As ecommerce entrepreneurs, we rely on automation and trust. A simple DNS misconfiguration can silently stop your store’s communication—and your sales—overnight. Take ten minutes to verify your authentication today, and you’ll save yourself hours of troubleshooting (and lost revenue) later.

Stay smart, stay authentic, and keep those customer connections strong!

6. FAQs About Email Authentication