There is no requirement to enter anything as part of your SPF record as this is handled by GroupBC themselves. In order to achieve DMARC compliance you will only have to configure DKIM.
GroupBC do support DKIM signing on behalf of their client domains. Please contact their support team using this email address [email protected] tand request DKIM signing to be implemented for your domain. They will them provide you with the necessary DNS records to enter in your DNS.
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