Article 50916 of comp.mail.sendmail:
Path: matra.meer.net!news1.best.com!news.maxwell.syr.edu!fu-berlin.de!news.belwue.de!not-for-mail
From: georgi@belwue.de (Juergen Georgi)
Newsgroups: comp.mail.sendmail
Subject: Re: Return-Receipt-To
Date: 3 Nov 1997 13:19:24 GMT
Organization: BelWue
Lines: 18
Message-ID: <63kj0s$b0u$2@news.belwue.de>
References: <345D967E.41C6@isd.uni-stuttgart.de>
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In article <345D967E.41C6@isd.uni-stuttgart.de>,
	Albrecht Melan <melan@isd.uni-stuttgart.de> writes:
> Hi there,
> 
>    running Sendmail 8.8.3/8.8.3 
>    how can  'Return-Receipt-To' headers be handled anyway ?
>    
>    The requesting site runs sendmail 8.6

sendmail 8.8.8 offers the unofficial and hidden option "RrtImpliesDsn". 
You need to compile with ENVDEF=-D_FFR_DSN_RRT_OPTION and add 

O RrtImpliesDsn=True

to your sendmail.cf. Option RrtImpliesDsn generates DSN when 
return-receipt-to is requested. I do not know how complete
RrtImpliesDsn is implemented. You will probably see it officially 
in 8.9.