How to Troubleshoot Email Delivery Failures

You’ve created a great email campaign. The content’s solid, the design looks sharp — but the results? Disappointing. If your emails aren’t getting opened or clicked, it might not be the message that’s the problem — it could be that your emails aren’t even reaching your audience.

Yes! Your emails might be bouncing.

This guide will walk you through exactly how to diagnose and resolve delivery issues using only Mailmodo.

Common causes of email delivery failure

There are multiple reasons why your emails would bounce. Here are some:

• Misconfigured domain authentication (SPF, DKIM, DMARC)

• Sending emails to unverified or purchased email lists

• Spam complaints in the past

• Low engagement rates in previous emails.

• Lack of domain warm-up

X steps to troubleshoot email delivery failures using Mailmodo

Whether it’s a misconfigured domain, poor list quality, or a reputation hit, Mailmodo gives you the visibility and controls to fix it fast and prevent future issues.

Step 1: Authenticate your domain properly (SPF, DKIM, DMARC)

Authentication is your first line of defense. Without properly configured SPF, DKIM, and DMARC records, inbox providers may reject or flag your emails as suspicious.

How to do it in Mailmodo:

• Go to Settings, and by default Sender domains section will open.

• Select the email address name you want to verify and open the three-dot menu.

• Choose Check DNS settings to review the current authentication setup. Confirm that the SPF record includes spf.mailmodo.com, that DKIM is verified, and that DMARC is configured with reporting and enforcement to safeguard your domain.

If issues continue, refer to Mailmodo’s SPF troubleshooting guide.

Step 2: Analyze bounce reports

Bounces provide direct feedback about why an email wasn’t delivered. Analyze the count and frequency of the bounces to ofo

How to do it in Mailmodo:

1. Go to the campaign and select a running campaign you want to check the bounce report on.

2. Check the Bounce reason report in Mailmodo, which shows the specific cause of each bounce.

3. Understand the type of bounce:

• Hard bounces occur when an address is invalid or no longer exists. Mailmodo automatically removes these addresses.

• Soft bounces are usually temporary, such as a full inbox or a server timeout.

5. Retry sending to soft bounce addresses later, and consider removing addresses that repeatedly bounce.

Step 3: Warm up your domain

New domains or IPs need time to earn trust. Without warming, you risk being throttled or flagged.

How to do it in Mailmodo:

1. Create your email campaign by opening the Campaigns tab in the Mailmodo dashboard.

2. On the final step, click Schedule Campaign from the dropdown menu.

3. Select Send in batches at regular intervals (up to 7 days) and define the recipients, hours, and days.

4. Preview the setup, confirm the details, and schedule your campaign.

Step 4: Verify and clean your email list

List quality is crucial. Old, purchased, or unverified lists can sabotage your delivery.

How to do it in Mailmodo:

1. Don’t upload purchased lists — ever

2. Validate addresses externally before uploading

3. Identify and suppress inactive users

• Use Mailmodo’s inactive contact management

5. Regularly prune contacts who haven’t opened in 60–90 days

Conclusion

Email delivery issues aren’t always obvious — but they’re always expensive.

Mailmodo gives you the visibility and control to fix the most common causes of failure, from authentication and domain reputation to AMP approval and list hygiene.

With the right process in place, your emails will land exactly where they’re supposed to — and start delivering the results they’re meant to.

Ready to troubleshoot smarter? Use Mailmodo’s built-in tools to deliver better, every time.