How to send an automatic reply email when a customer replies to an email sent with Klaviyo?

Hey @Manel 

Welcome to the community and congrats on your first post!

Regrettably, Klaviyo's platform does include that kind of service - this kind of email would need to be set up with your email service provider (Gmail, Yahoo or Outlook). Klaviyo can only send automatic flow messages in response to events, like subscribing or placing an order. It's not possible to trigger on an email response, as we don't receive that data. I will send this feedback to our product team for future evaluation on your behalf!

Thanks again for being part of the Klaviyo community!