When an agent replies to a question then NeetoDesk sends an email to the customer. When that customer replies then those emails lands at NeetoDesk and those emails are processed. This is how things work "by default".
It works like this because when customer hits "reply" then then "Reply-To" field is set to NeetoDesk email by default. If you have configured Google mail, outlook etc then that email will be the default "Reply-To".
However for any reason you want the customer replies to not to come to NeetoDesk then you can provider an email address after checking the checkbox and all customer replies will go that email address.
Please note that checking that checkbox means NeetoDesk will NOT be getting the customer replies and NeetoDesk will not be able to do its job properly. So please think twice before checking that box.
When using a custom reply-to email, incoming customer replies will
be sent to your custom email address instead of NeetoDesk. To ensure these
emails are still processed as ticket updates, you must set up email forwarding
from your custom reply-to address back to your NeetoDesk mailbox.