What is an email subdomain?
An email subdomain is a DNS subdomain used specifically for sending email. Instead of sending from your root domain (e.g. example.com), you send from a dedicated subdomain such as:
mail.example.comnews.example.comtx.example.commarketing.example.com
The subdomain appears in the visible From: address and is also used for SPF and DKIM alignment.
Why use email subdomains?
- Isolate reputation. Problems in one email stream (e.g. marketing complaints) won’t damage others (e.g. transactional mail).
- Protect the root domain. Your main domain used for corporate email and your website stays safer.
- Different DMARC policies. You can apply stricter policies to transactional mail and more gradual ones to marketing.
- Better visibility. Reputation, bounce rates, and engagement metrics can be tracked separately per stream.
Common Subdomain Patterns
tx.example.com— Transactional emails (receipts, password resets, order confirmations)news.example.com— Newsletters and editorial contentmarketing.example.com— Promotional and campaign emailssupport.example.com— Customer support and service repliesnotify.example.com— Product alerts and system notifications
For detailed guidance on naming conventions, DNS setup, DMARC configuration, and warming strategies, see the Email Subdomain Strategy Guide.