Eunice here from the Shopify team. Welcome to the Community, and thanks for posting!
From your message, it sounds like you're wanting to send an automated email containing a discount code to subscribers when they sign up. Is that right?
Automated emailing isn't a feature of Shopify Email just yet. I can confirm it's sitting fairly high on the feature request list though. We realize this is a huge need for our Merchants, and we care about that. With your help we could push this feature request even higher, would you like me to add your vote?
In the meantime, I recommend using a third-party app such as Seguno. It's free to use for the first 250 subscribers, and it allows you to send the following automated emails:
There are a few other email marketing apps that do the same job which you can view here, but, I recommend Segno because I've used it myself and love it. They have an awesome support team too!
Let me know about that vote.
@gwillo Wonderful. I have gone ahead and sent you an email to your community email address. I'll just need to grab a couple of details from you to add you to the feature request vote.
Catch you there!