Hi, @Shannalynn01
Greetings, and thanks for posting!
DMARC is a record that Yahoo, and Gmail require be added to your DNS settings if you use a custom email such as hello@yourstore . If you aren’t using a custom email, or you don’t add a DMARC record to your domain, Shopify will use store@shopifyemail.com as your sender email.
I notice you mention your domain ends in .myshopify.com still. If that is the case, you wouldn’t need to add DMARC as you don’t have a custom domain and the store@shopifyemail.com would be used. If, however, you do have a custom domain hosted by Shopify, you should already have a DMARC added to your DNS settings by default. You can check this by heading to Settings > Domains > Domain Settings > DNS Settings > Then scroll down and you should see the DMARC record.
If you are using a third party domain you can use our guide here to add the DMARC record to your DNS Records.
I hope that helps!