At present, we don't support the customization of TXT records for email authentication, including DMARC record updates. DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an essential email authentication protocol designed to protect domains from unauthorized use, such as email spoofing.
Typically, merchants would need to update their DMARC records by adding TXT records to their DNS settings. These records provide critical information that email servers utilize to determine the treatment of emails originating from the domain.
However, our current system does not offer support for custom TXT records for email authentication purposes.