Hey, @KalvinT .
Thanks for reaching out and posting this question!
If you’re using a third-party domain and you have your own email hosting, then it’s possible that the emails are being blocked or flagged as spam by the recipient’s server. In order to resolve this issue, you’ll need to authenticate your third-party domain and add records to connect with the Shopify Sender Policy Framework (SPF) and Domain Keys Identified Mail (DKIM) records. If you need help with adding the CNAME and DMARC records to your domain, then you can also contact your domain provider for further assistance.
That being said, I noticed that you’re a new member of our Shopify Community and I’d love to hear more about your business! What kinds of products are you selling? Do you have a marketing plan prepared for your store?