Freemius uses SendGrid for all of the transactional sending to users and customers, but in order to ensure reliable email deliverability through the service, users need to configure Freemius with SPF and DKIM. To do this you will have to add an inclusion for your SPF record, and add a set of additional CNAME records in your DNS for DKIM that is provided to you by Freemius.
The SPF mechanism that you will have to add to your DNS (if you already have an SPF record) is:
Login to the Developer Dashboard.
Navigate to the 'EMAIL ADDRESSES' section.
Click the 'AUTHENTICATE DOMAIN WITH DKIM' button to initiate the authentication process.
Enter the domain you send emails from and click 'AUTHENTICATE:'
SendGrid will create a set of CNAME records you’ll need to add to your host’s DNS section:
Once all records are added, check the “I’ve added these records” checkbox and click VERIFY.
Create a free OnDMARC account to test your configuration.