change the return path based on domain

we are planning on moving a web site from one hosting company to another, both services being dedicated linux servers, but the new company's host is not accepting "-r" argument of sendmail.

one of our developers is normally using sendmail with -r option, which overrides the default Return-path an the following works on the old dedicated server

/usr/lib/sendmail –t –r web@[domain].com

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how can we specify different return path when sending e-mails. there are two domains on our host and depending on the domain name we want the returns to be handed to web@ the respective domain.

on the new host however we get this

sendmail: illegal option -- r
sendmail: usage: sendmail [ -t ] [ -fsender ] [ -Fname ] [ -bp ] [ -bs ] [ arg ... ]

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there are also various qmail processes running, which we did not have on the old server.