I need a way to configure sendmail to set the envelope sender of every message to a fixed value (say email@example.com). Note that this is not answered by any of the MASQUERADE features/macros (that I know of): I want to also override the envelope user and set it to a fixed value.
EDIT: Also, I do not want to masquerade the header sender. So GENERICSTABLE + MASQUERADE_ENVELOPE does not cut it, either. What I need is the equivalent of command line
sendmail -f firstname.lastname@example.org
(Rationale: I am forced - by the customer - to go through an authenticating relay which insists on having a given envelope sender address - and no, I am not trying to circumvent any antispam measure, I merely want to send root's mail - and other administrative stuff - offsite. It is an application server, and all the mail is originated by servers, but sender addresses need to be meaningful nevertheless)