"Presumably the customer left their real email address in their reply by accident."
Have to be quite careful about this. Avoid--I think this was it--using Gmail to reply to your own email (like when someone doesn't follow up on it), or it'll leak.
Also have to be incredibly careful Mail (macOS, even iOS IIRC) doesn't change your Sent From address from the just-generated Hide My Email address to your default with no warning or rationale. That is a HORRIBLE bug.
Jeff Johnson is most excellent.
"Presumably the customer left their real email address in their reply by accident."
Have to be quite careful about this. Avoid--I think this was it--using Gmail to reply to your own email (like when someone doesn't follow up on it), or it'll leak.
Also have to be incredibly careful Mail (macOS, even iOS IIRC) doesn't change your Sent From address from the just-generated Hide My Email address to your default with no warning or rationale. That is a HORRIBLE bug.