How Coding Blocks Improved Email Deliverability and Revived Engagement

Challenge

Coding Blocks is a leading edtech company that empowers students with programming skills through a mix of online courses, live training, webinars, and scholarship programs. Email has been one of their most reliable channels for communication and promotion and is used to drive course enrollments and webinar registrations.

A few months ago, their email performance declined: open rates among active users fell from 20% to 10%, and an increasing number of messages were being flagged as spam. As a result, their domain reputation also fell to low.

Solution

Mailmodo stepped in with a diagnostic and troubleshooting plan to restore deliverability.
Mailmodo’s team audited Coding Blocks’ email campaigns and identified the root causes of the poor performance:

• Coding Blocks was sending image-heavy campaigns that triggered spam filters (Gmail flags high image-to-text ratios) and hurt engagement due to slow loading and accessibility issues.
• They had also scaled up their sending volume without warming up their domain, which can trigger spam filters used by email providers (such as Gmail, Outlook, Yahoo, etc.), causing their emails to land in recipients' spam folders instead of their inboxes.

To address these issues, Mailmodo recommended and implemented the following steps:

• Email content restructuring: They transitioned Coding Blocks away from image-only email campaigns and created text-rich, educational emails using Mailmodo’s drag-and-drop builder.

• Audience segmentation: Mailmodo helped Coding Blocks identify their most engaged subscribers — those who had actually opened their emails in the past 30 days — and planned to send emails to only them for a few days.
  This strategy helps rebuild trust with email providers by demonstrating that people genuinely want to receive and engage with emails.

• Domain warm-up and ramp strategy: Instead of immediately sending large batches, Mailmodo's fragmented scheduling helped Coding Blocks spread their emails throughout the day and gradually increase their sending volume.
  

This approach signals to email providers that Coding Blocks is a trustworthy sender, not a spammer.

Results

After implementing these best practices, Coding Blocks saw measurable improvements:

• Open rates among active users improved drastically and restored to 20%.
• The domain reputation improved to ‘medium’ and stabilized in just a period of 45 days.
• CTR too increased drastically with the change in content, and website traffic driven by email increased 5X

Mailmodo helped us fix deliverability and visibility issues by combining practical content guidance with powerful product features. Their team showed us why our image-heavy emails were hurting inbox placement, then helped rework content using the drag-and-drop editor and templates, and set up behavioral Segmentation to target high-intent users. With those changes, our open rates recovered from ~10% to ~20% and our domain reputation stabilized. Ashutosh, Digital Marketing Strategist, Coding Block

Key learnings for your next campaign

Use text-based layouts instead of image-heavy designs: Rather than putting content in images, use well-designed text layouts that are accessible and fast-loading. Mailmodo makes it easy to create beautiful email designs with clean layouts and interactivity—all without relying heavily on images.
Image-heavy emails load more slowly, reduce accessibility, and are more likely to be flagged as spam. Focus on useful content, add visuals and interactive elements contextually, and provide value through your email campaigns rather than treating them like ads.

Warm up domains and segment your audience before scaling : If you notice a sudden dip in your domain reputation, pause all campaigns and segment your contacts. Focus on sending campaigns only to high-intent users (recent email openers) for a few days, then gradually increase volume to your full list. You can utilize features like fragmented scheduling on Mailmodo to automatically distribute sends throughout the day, maintaining your domain reputation without manual intervention.