How to detect email deliverability issues before they hurt sales

The subject line is compelling. The offer is irresistible. The timing is just right.
But somewhere between hitting “send” and reaching your customers’ inboxes, your messages vanish into the digital void.
By the time you notice the plummeting open rates and missed sales opportunities, the damage is already done.

This is a reality many businesses face. Last quarter, a growing e-commerce brand lost over $50,000 in potential revenue before discovering its promotional emails were landing in spam folders.
The worst part? The warning signs were there weeks before sales took a hit. 

Email deliverability issues rarely strike without warning. There are clear indicators that can alert you to problems before they impact your bottom line. Let’s look at exactly how to spot these warning signs and take action before you suffer.

1. Monitor Key Performance Metrics

Regularly tracking specific email metrics provides early warnings of deliverability issues:

• Bounce Rates: Keep these under 2% - anything higher indicates list quality issues or potential blocking. Monitor both hard bounces (invalid addresses) and soft bounces (temporary failures).
• Open Rates by Domain: Sudden drops, especially with specific email providers (Gmail, Yahoo, etc.), often signal that your messages are being filtered to spam.
• Spam Complaint Rates: Watch this closely - anything above 0.1% demands immediate attention. Rising complaints often precede major deliverability problems.

2. Authenticate Your Emails Properly

Email authentication failures are often the first sign of impending deliverability issues:

• SPF (Sender Policy Framework): Ensures only authorised servers can send emails from your domain.
• DKIM (DomainKeys Identified Mail): Adds a digital signature verifying your emails' authenticity.
• DMARC (Domain-based Message Authentication): Provides instructions to ISPs on handling emails that fail authentication checks.

Use mail-tester.com to verify that these records are properly configured regularly. Even small authentication gaps can trigger spam filters.

3. Implement Engagement Monitoring

Low engagement is a leading indicator of deliverability issues. Set up tracking for:

• Click-through rates across different segments
• Reply rates for important campaigns
• Unsubscribe patterns and timing

4. Maintain a Clean Email List

Regularly updating your email list ensures you're reaching engaged recipients:

• Remove Inactive Subscribers: Eliminate addresses that haven't engaged in over six months.
• Validate New Addresses: Use double opt-in methods to confirm validity.
• Avoid Purchased Lists: These contain outdated contacts that damage your sender's reputation.

5. Optimize Email Content

The content of your emails significantly impacts deliverability:

• Avoid Spam Trigger Words: Phrases like "free," "buy now," or "limited time offer" can activate filters.
• Balance Text and Images: Maintain a 60:40 text-to-image ratio.
• Include Clear Unsubscribe Options: This reduces the likelihood of spam reports.

6. Use Dedicated Monitoring Tools

Leverage these essential tools for early warning:

• Google Postmaster Tools: Provides direct insight into how Gmail views your sending reputation.
• MXToolbox: Helps detect if you've been added to any blacklists - often before email providers start blocking.
• Seed List Testing: Services like GlockApps let you proactively check inbox placement across providers.

7. Set Up Automated Alerts

Create alerts for:

• Sudden spikes in bounce rates
• Drops in open rates below historical averages
• Appearance on any blacklists
• Authentication failures
• Unusual sending volume changes

8. Take Immediate Action on Warning Signs

When you detect issues:

1. Immediately pause high-volume sending
2. Investigate authentication problems
3. Clean your email list, focusing on recent bounces
4. Review recent content changes that might trigger spam filters
5. Check IP and domain reputation scores

Expert Setup and Monitoring

While these monitoring systems are crucial, setting them up correctly requires technical expertise. BlueOshan's Email deliverability (ED) experts can:

• Configure comprehensive monitoring across all major email providers
• Set up custom alert thresholds based on your business needs
• Implement automated reporting dashboards
• Create emergency response protocols
• Establish baseline metrics for your industry

Remember, it's much easier to prevent deliverability problems than to fix them after they impact your business. Regular monitoring and quick response to warning signs will help maintain consistent inbox placement and protect your email marketing ROI.

Regular monitoring and quick response to warning signs will help maintain consistent inbox placement and protect your email marketing ROI. 

Ready to protect your email deliverability? Contact BlueOshan's team for a comprehensive monitoring setup that will ensure your messages land in the inbox, avoiding the spam folder right away.