Confirmation and success emails are sending via mailChimp service. So, there is need to transfer coupon's code to mailchimp side.
Magento side configuration
Newsletter confirmation has to be enabled.
- Go to: Stores >> Configuration >> Customers >> Newsletter
- Set Need to confirm? to YES
- Save configuration.
MailChimp side configuration
- Go to Mailchimp page and login to your account.
- Go to: Lists >> Click on your list >> Sign Up Forms >> Form Builder
- Set Option "Forms and response emails" to "final welcome email" and check "Send a final welcome email" option
- Go to: Lists >> Click on your list >> Settings >> List fields and *|MERGE|* tags >> Add a Field
Enter the following information
Field label: Coupon Code
Put this tag in your content: COUPON
Additional fields configuration
Additional fields are working the same as coupon’s code. Use additional fields name for mapping fields instead of np_discount_code.