Should you use subdomains to send emails?

Yes, using subdomains for email sending can be highly beneficial, especially for large campaigns or cold outreach. Here’s how subdomains can help, along with some best practices:

Benefits of using subdomains

1. Protects primary domain reputation
   • Sending high volumes of marketing or cold emails from a primary domain risks lowering its sender reputation if engagement drops or complaints increase. Using a subdomain (e.g., marketing.yourdomain.com) isolates these activities, keeping your main domain reputation secure for essential emails, like customer service or transactional messages.
2. Improves deliverability control
   • Subdomains allow you to build a separate reputation with email service providers (ESPs) based on the type of emails you’re sending (e.g., newsletters vs. cold outreach). ESPs treat each subdomain individually, so well-maintained subdomains can help improve deliverability for different types of campaigns.
3. Organizes different email streams
   • Separating transactional emails, marketing emails, and customer service emails by subdomain provides better organization and simplifies tracking engagement and performance across various email streams.

Best practices for using subdomains

• Authenticate each subdomain separately: Set up SPF, DKIM, and DMARC records for each subdomain to ensure ESPs recognize them as legitimate. This helps establish trust and improve deliverability.
• Warm up each subdomain individually: If you’re starting a new subdomain for cold emails or marketing campaigns, gradually increase sending volume to build its reputation. Using tools like Warmup Inbox can automate this process and protect deliverability.
• Monitor engagement metrics by subdomain: Track open rates, click-through rates, bounce rates, and complaints separately for each subdomain to catch any issues early and adjust as needed.

Summary:

Using subdomains for email sending helps protect your main domain’s reputation, improves deliverability control, and keeps your email streams organized. For effective cold emailing or large marketing campaigns, setting up a dedicated subdomain is a smart, reputation-safe approach.