This one will be short. If you want to customize you default Shopify notifications (and you’d better do that) and create beautiful responsive html emails, you should definitely check out Klaviyo. They’ve created a few ready Shopify email templates, which could be used for free. There’s even no need to install any app.
Just create an account, go to Email Templates → Create Template and search for Shopify Templates section:
When you’ve chosen your first template, you need to customize it with your company name, add some text that transmits your unique brand message, add links to social media and hit ‘save’. Get back to the list of templates, export it and insert into your Shopify notification settings:
Don’t forget to send yourself a test email and look how lovely it is now.
If you need more instructions, here’s a full guide on Klaviyo docs site. Also check out their blog about email marketing. Tons of useful advice.
P.S. I know that there are people selling Shopify email templates like that for around 40$. A penny saved is a penny gained 😉