You can add the following rule to the *check_mail* hook in sendmail
R$*<> $#error $@ 5.7.1 $: "551 You must provide a proper from address"
This will require the sender to provide something as a mail from: value
and then any content given will be checked by the regular tests that you
provide. See sendmail.org for additional info about the hook.
<><Randall Grimshaw, Network Programmer, Syracuse University, 315-443-5779
On Fri, 6 Mar 1998, Chris Brenton wrote:
> The blank return path bothered me. I've tested this off of a few mail systems
> and was surprised to see that all of them would accept a blank "mail from:"
> line. Are there any firewalls out there that would kick this message out by
> default? Mail systems?