If you’re facing an issue where your order notifications are going to spam, then make sure your SPF record is configured correctly.
If you are pointing your Name servers to BigCommerce – then this issue won’t arise because SPF records are automatically setup correctly in that cause. But In this case, if you are using service like Gmail, outlook etc for your email – then you’ll need to add their SPF record correctly.
Here is the documentation provided by BigCommerce.
If your Name Servers are managed outside of BigCommerce, then you need to make sure that you do add BigCommerce SPF record in your DNS records.
v=spf1 +a +mx include:spf.bigcommerce.com ~all