Improve Email Deliverability with Custom Tracking Domains
How we improved inbox placement by 15-20% for a fast-growing email campaign platform by implementing automated SSL and branded tracking domains.
Overview
A fast-growing email campaign platform was facing deliverability issues across major inbox providers. While SPF, DKIM, and DMARC were correctly configured, emails still ended up in spam, especially for Gmail and Outlook users.
The root cause was identified: tracking links and open pixels were pointing to third-party domains, which didn’t match the sender’s email domain.
By implementing a Custom Tracking Domain (CTD) system using CNAME records and automated SSL provisioning, we were able to significantly improve email inbox placement and enhance recipient trust.
Challenges Identified
The client faced several technical and usability challenges that were impacting their email deliverability.
Domain Mismatch in Tracking Links
Emails sent from addresses like john.doe@valensdatalabs.com contained links from domains like track.example.com, creating trust issues with filters.
High Spam Placement Rates
Despite valid DNS setups, major inbox providers flagged emails due to third-party redirects and embedded tracking domains.
Manual SSL Management Overhead
Using branded domains required SSL certificates, but manually issuing and renewing them for every client was not scalable.
Complex DNS Configuration
Non-technical users struggled to configure DNS records correctly, leading to setup failures and delays.
Solution
We implemented a comprehensive Custom Tracking Domain (CTD) system with automated SSL provisioning.
Key features
Custom Domain UI for Users
Built a clean frontend interface allowing users to add and manage multiple CTDs.
- Enabled support for campaign-specific domains and multi-brand tracking
- Simplified the process with step-by-step guidance and visual status indicators
CNAME Validation Using Public DNS APIs
Validated CNAME setup through DNS-over-HTTPS (DoH) APIs.
- Checked for record conflicts (e.g., existing A/TXT records)
- Suggested alternative subdomains when the preferred one was already in use
Automated SSL Installation
Triggered a Jenkins job post-validation to provision SSL automatically.
- Script handled NGINX config and Certbot certificate setup
- Certificates auto-renewed using Certbot’s cron jobs and renewal hooks
NGINX Configuration for Custom Domains
Configured NGINX with individual server blocks to support CNAME-based custom tracking domains.
- Ensured secure HTTPS delivery of tracking pixels via the user’s subdomain
Additional Enhancements
Flagged potential wildcard DNS conflicts (*.domain.com) that blocked specific subdomain use
- Built pre-checks to warn users and suggest valid alternates
- Added inline helper text for DNS config to guide non-technical users
Additional Enhancements
Conflict Detection for Wildcards
Flagged potential wildcard DNS conflicts (*.domain.com) that blocked specific subdomain use and suggested alternates.
UI Improvements to Reduce Errors
Added inline helper text for DNS config and live domain status with step-wise validation.
Scalable Architecture
NGINX config templated to support 1,000s of subdomains securely using SNI to dynamically select SSL certificates.
Benefits Realized & Measured Impact
By implementing Custom Tracking Domains with automated DNS validation, SSL provisioning, and branded tracking URLs, we achieved the following improvements:
Deliverability Improved
Achieved higher inbox placement across Gmail and Outlook by eliminating mismatched tracking domains.
CTR Increased
Branded tracking domains built user trust, reducing hesitation to click on links and boosting engagement.
Lower Spam Complaints
Aligned sender and tracking domains lowered spam flag triggers, resulting in fewer flagged emails.
Setup Success Rate
Automated validation and guided domain setup drastically reduced misconfiguration and support queries.
Zero Manual SSL
Migrated from manual SSL handling to full automation with Jenkins and Certbot.
Faster Onboarding
Users could complete domain setup in under 15 minutes compared to 2–3 days previously.
Conclusion
By aligning the tracking infrastructure with sender domains using Custom Tracking Domains and automating SSL setup, we solved a major deliverability bottleneck.
This solution not only reduced spam flagging and increased engagement, but also delivered a smoother onboarding experience for clients.
If you’re sending emails on behalf of clients or brands, CTDs are a critical step in maintaining trust, improving engagement, and scaling securely.
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