Re: About the use of the "return-receipt-to" ....

> > What is the "return-receipt-to" field ?
>   See  RFC 3464  (and RFC 2076)
>
> > Some MTA (eg : Lotus) interpret that field as a MDN request.
> > Is it legal and clearly defined in RFC ?
>   Completely non-standard.
not only that, but it's completely incompatible with the original use of the
field, which was to request a delivery report, not a receipt notification.

return-receipt-to fields should be ignored, or deleted.