Hey, @JINCHENLONG .
Thank you for reaching out and posting this question!
I understand you’re looking for an app that allows you to send emails to customers after their purchase, so you can capture the information of their device(s) for servicing or repairing. There are plenty of third-party mailing apps, such as Klaviyo or Omnisend, which offer automation for emails. However, if you want to use a mailing app for sending and collecting forms, then you may want to speak to the developer on how to do this using their app. If you need any help with a third-party app, the app developer is always available to assist you. Simply reach out to them directly through the contact information found in the Support section of their app’s page.
That being said, you can also consider adding a form onto your product or cart pages as opposed to sending the forms using emails. This way, customers can provide all the information as they check out and reduce the number of back-and-forth emails. If you’d like to explore adding forms to your store, then please check out our list of form builder apps.
Since you’re offering repair services, then it’s possible that some customers may have additional questions or they may want to check on their repair status. Have you considered using something like Shopify Inbox (not Shopify Email) to interact with customers live on your store?