About Configuring DMARC Subdomains for IBU Branding Emails
If you have DMARC enforcement enabled (p=quarantine or p=reject), configuring a DMARC subdomain for IBU branding emails is required to meet DMARC requirements for SPF alignment.
This configuration:
provides a location to send bounce-back emails.
allows Barracuda MSP to update the header from and send from domains.