I have long wondered why emails are sent by companies from noreply, with no custom reply field. The email typically warns you not to reply to this email but if you do want to contact them, them send an email to <this> place.
I have to strongly question the competence of anyone using this system. They have sent you an email, typically for a specific purpose, often including things like transaction ids. Your next step if you want to contact them is to either begin a whole new email chain, or fill out a form, enter into a ticket system or possibly even call them.
All of that could be avoided by filling the reply field with a transaction unique address. Or alternatively, they could use a common reply address and fill the subject line with a unique id.
Why do you think so many companies do this with electronic business?