Who This Is For / When to Use
This article is for Kyrios account owners and admins who use account-created dedicated sending domains and want to ensure consistent sender identity and deliverability when DMARC alignment fails.
Use this when:
You send email from a dedicated domain in Kyrios.
You want a controlled fallback sender for DMARC failures.
You are troubleshooting inconsistent “From” values in delivered emails.
What Default Headers for Dedicated Domains Do
Default headers define a fallback From Name and From Email that Kyrios applies only when DMARC alignment fails for an email sent from a dedicated domain. These headers do not override custom headers when DMARC passes.
This protects deliverability while preserving branded sender information whenever possible.
Where Default Headers Are Applied
Default headers apply only to:
Dedicated sending domains created inside the Kyrios account
Emails sent through the Kyrios SMTP Service
They do not apply to:
Shared sending domains
External SMTP providers
Emails where DMARC alignment passes successfully
How to Set Default Headers for a Dedicated Sending Domain
You configure default headers from the SMTP Service domain menu.
Steps
Open Account Settings from the bottom-left menu.
Navigate to Email Services → SMTP Service.
Select Dedicated Domain and IP.
Locate the dedicated domain you want to configure.
Click the three-dot (⋯) menu next to the domain.
Select Set Headers.
Enter the fallback From Name.
Enter the fallback From Email.
Click Save.
When the Fallback Header Is Used
The fallback header is applied only under both of the following conditions:
DMARC alignment fails for the message (SPF or DKIM misalignment).
The email being sent does not already pass DMARC with its original headers.
If DMARC passes, Kyrios sends the email using the original From Name and From Email without modification.
What Happens If No Default Header Is Set
If no default header is configured and DMARC alignment fails:
The email may fail authentication checks.
Deliverability risk increases.
The message may be rejected or filtered as spam by receiving servers.
Setting a default header prevents this failure state.
Common Issues and Fixes
Emails are using the fallback header unexpectedly
Cause: DMARC alignment is failing for the sending domain.
Fix:
Verify SPF includes Kyrios sending servers.
Confirm DKIM records are published and valid.
Recheck DNS after recent domain or provider changes.
“Set Headers” option is not visible
Cause: The domain is not an account-created dedicated domain.
Fix:
Confirm the domain was created inside Kyrios.
Shared domains cannot use custom default headers.
Deliverability issues persist even with fallback headers
Cause: Underlying DMARC or DNS configuration issues.
Fix:
Review SPF, DKIM, and DMARC records together.
Ensure only one SPF record exists.
Confirm DMARC policy syntax is valid.
Best Practices
Always set a branded From Name and monitored From Email.
Review DMARC, SPF, and DKIM whenever DNS changes are made.
Monitor fallback usage; frequent fallback indicates authentication issues.
Use a real inbox address for the fallback email to handle replies or bounces.