The Default Domain setting in Twilio SendGrid's Sender Authentication determines which authenticated domain is used to sign or brand your outgoing emails and links when Twilio SendGrid cannot find an exact match for the email's "From" address.
Question
How does the Default Domain setting work when used in Sender Authentication
Product
Twilio SendGrid
Environment
Twilio SendGrid Console
Answer
Automatic Fallback:
When you send an email, Twilio SendGrid compares the domain in your "From" address (e.g., sender@company.com) against all authenticated domains in your account.
- If a matching domain exists: Twilio SendGrid uses that specific domain’s authentication (DKIM/SPF).
- If no match exists: SendGrid falls back to your designated Default Domain to sign the message.
One Active Default:
You can authenticate multiple sending domains on a single account, but only one domain can be designated as the default at any given time.
Additional Information
Primary Domain: Set your primary, highest-volume, or most trusted domain as the default to ensure maximum deliverability if an unauthenticated "From" address is accidentally used in an application.
Subusers: Parent accounts can assign authenticated domains as default for subusers, ensuring subuser traffic remains authenticated without giving them permissions to modify DNS settings.
Link Branding: Setting a Default Domain for a domain verified in Link Branding follows the same logic. If a matching domain exists, Link Branding will brand links with that specific domain. If no match exists, than the links will be branded with the domain set as the Default Domain.