Hi Chad,

thanks for the clap and asking question!

For your question, when you send an email with SendBetteremail action, are you logging the email as EmailMessage object? if yes, there will be MessageIdentifier stored in EmailMessage record, see this MessageIdentifier field as reference https://developer.salesforce.com/docs/atlas.en-us.object_reference.meta/object_reference/sforce_api_objects_emailmessage.htm . To handle reply from your respondent, you can use the email subject as your criteria for routing to the right process, for example everytime you send a survey email, the subject will always be "Survey Email from Chad" and once you catch that kind of email message with your email service, you can query which EmailMessage record has the same Messageidentifier and you'll get the related to field, from there you can do your own logic with the case

I hope that makes sense

thanks