DMARC, which stands for “Domain-based Message Authentication, Reporting & Conformance”, is an email authentication, policy, and reporting protocol.
To improve the security of emails, many popular email inbox providers (Gmail, yahoo, etc) will display email readers a warning if the sending address of the email is not validated by the DNS records of that domain.
This protects users from email "Phishing" attacks in which a 3rd party will attempt to collect login credentials by pretending to be an authorized company user.
This is how it would look for your partners:
Because PartnerStack sends emails on behalf of your company's domain name, you'll need to take a few simple steps to allows us to send your behalf.
Step 1. Contact Support
Contact the PartnerStack support team at firstname.lastname@example.org and mention "DMARC".
Support will return you the CNAME records you'll need to add to your DNS records
Step 2. Add CNAME records to your DNS
Add the three CNAME records to your DNS as given to you by support.
You may need to contact a technical resource at your company to have these records added.
Once added, please wait 30 minutes and then let support know
Step 3. Verification
Support will verify and let you know if the records have been added correctly.
With the correct DNS records added, PartnerStack email to your partners will be signed and verified by your Domain allowing your emails to be successfully delivered to your partners.