Should I use subdomains or separate root domains?

You're choosing between convenience and isolation. Subdomains are easier to manage but share reputation with your main domain. Separate root domains are more work but give you real protection if something goes wrong.

Subdomains (outreach.company.com) are simpler to manage:

You handle DNS in one place. Your brand connection stays intact. You can configure separate SPF, DKIM, and DMARC records for the subdomain. But here's the catch: if your outreach subdomain gets listed on Spamhaus or develops a bad reputation, it can drag down your main domain's reputation too. They're not completely isolated.

Separate root domains (companyhq.com, trycompany.io) give you real isolation:

And each domain has its own reputation profile. If one burns, your main brand domain stays clean. Gmail and other providers can't as easily connect them. But you're managing more infrastructure. More domains to register. More authentication records to configure. More moving parts.

Here's the decision framework:

If you're sending high-volume cold outreach with real reputation risk, use separate root domains. Your main brand is worth protecting. If you're doing lower-volume, lower-risk segmentation, subdomains are fine. And no matter what you choose, keep your transactional email (password resets, order confirmations, that stuff) on completely separate infrastructure from cold outreach.

Use our SPF checker to validate your domain configuration before you start sending.