Introduction

Email deliverability is critical for ensuring your messages reach recipients' inboxes rather than spam folders. One key decision in email marketing and newsletters is whether to use your primary domain (e.g., firstname@companyname.com), a secondary domain (e.g., firstname@companyname2.com), or a subdomain (e.g., firstname@comms.companyname.com). Each option has distinct advantages and disadvantages that impact sender reputation, branding, and overall effectiveness.

Understanding Email Deliverability

Email deliverability refers to the ability of an email to successfully reach the recipient's inbox. Several factors influence deliverability, including:

  • Sender reputation (IP and domain reputation)

  • Email authentication protocols (SPF, DKIM, DMARC)

  • Engagement rates (open rates, click-through rates, spam complaints)

  • Spam filters and blacklists

  • Sending infrastructure (dedicated vs. shared IPs, email sending platforms)

Using the Primary Domain (companyname.com)

Advantages

  1. Brand Recognition & Trust – Emails from the primary domain are immediately recognizable and trusted by recipients.

  2. Higher Engagement – Customers are more likely to engage with emails that come from the official company domain.

  3. Unified Reputation – A single, well-maintained domain with strong authentication (SPF, DKIM, DMARC) can help maintain a solid sender reputation.

Disadvantages

  1. Risk to Business-Critical Emails – If marketing emails trigger spam complaints, the entire domain’s reputation could be impacted, affecting transactional and business-critical emails.

  2. Potential for Blacklisting – If email campaigns cause issues (e.g., excessive unsubscribes, spam reports), the primary domain could be blacklisted, harming all email communications.

  3. Lower Risk Isolation – Issues with marketing emails affect all email types, including customer support, sales, and internal communications.

Using a Secondary Domain (companyname2.com)

Advantages

  1. Risk Isolation – If marketing emails cause deliverability issues, they won’t impact the primary domain’s reputation.

  2. Better Segmentation – Allows clear differentiation between marketing and transactional emails.

  3. Avoids Primary Domain Blacklisting – Any issues (e.g., excessive spam complaints) affect only the secondary domain, keeping the main domain secure.

Disadvantages

  1. Lower Trust & Engagement – Recipients might be unfamiliar with the secondary domain and less likely to engage.

  2. Brand Confusion – Customers might not recognize the sender, leading to lower open rates.

  3. Reputation Building from Scratch – The secondary domain must build its own sender reputation, which takes time and effort.

Using a Subdomain (comms.companyname.com)

Advantages

  1. Reputation Isolation – A subdomain has a separate sender reputation from the main domain but still benefits from the parent domain’s credibility.

  2. Brand Recognition – Since it contains the primary domain (companyname.com), it retains brand association and trust.

  3. Easier Management – SPF, DKIM, and DMARC can be customized per subdomain to optimize deliverability.

  4. Improved Segmentation – Different subdomains for different types of emails (e.g., marketing.companyname.com, support.companyname.com) improve deliverability management.

Disadvantages

  1. Requires Careful DNS Configuration – SPF, DKIM, and DMARC records must be set up correctly for each subdomain.

  2. Potential Reputation Contamination – While separate, a subdomain’s poor reputation can still impact the root domain’s overall reputation.

  3. Limited Isolation Compared to Secondary Domains – While it offers some isolation, it’s not as protective as using an entirely separate domain.

Best Practices for Email Deliverability

  1. Authenticate Your Emails – Implement SPF, DKIM, and DMARC to prevent spoofing and improve deliverability.

  2. Monitor Sender Reputation – Use tools like Google Postmaster Tools, Microsoft SNDS, and MXToolBox.

  3. Warm Up New Domains & IPs – Gradually increase email volume to build a positive sender reputation.

  4. Segment Email Sending – Use different domains/subdomains for marketing, transactional, and customer service emails.

  5. Maintain List Hygiene – Regularly clean email lists, remove inactive subscribers, and avoid purchased lists.

  6. Ensure Compliance – Follow GDPR, CAN-SPAM, and other email regulations.

  7. Use Dedicated IPs if Needed – For high-volume senders, using a dedicated IP prevents reputation dilution from shared environments.

Conclusion

Choosing between a primary domain, secondary domain, or subdomain for email marketing depends on your risk tolerance, branding needs, and deliverability strategy.

  • Primary domains offer trust and engagement but pose risks to business-critical emails.

  • Secondary domains isolate risk but require reputation-building and may reduce engagement.

  • Subdomains provide a balance between brand recognition and reputation isolation, making them a solid choice for many businesses.

By carefully configuring your email infrastructure and following best practices, you can optimize email deliverability while protecting your sender reputation.