[RFC822](http://www.freesoft.org/CIE/RFC/822/28.htm) on `Return-Path:`:

> 
> This field is added by the final transport system that
>  delivers the message to its recipient. The field is intended
>  to contain definitive information about the address and route
>  back to the message's originator.
> 
> 
> 

So how come some e-mails have two of them? (In my sample, usually one at the end and one at the start, from which I assume that client added it there.) Isn't there *only one* originator?

Is that a bad habit of some clients?