>>There is one thing that I've been meaning to look into though. Sendmail -
>>the most used MTA on the Internet blindly accepts mail from anybody for
>>anybody. I want to put an end to this. I've been meaning to look into how
>>much work it would be to make Sendmail refuse to accept a peice of mail not
>>destined for a user of any of the domains it is serving. (i.e. the
>>contents of the "w" macro).
>Can't do this without changing the standard first -- this is a defined
>feature of SMTP-based mail systems. Probably hopeless.
This is true, but...
Nothing stops you from refusing SMTP connections from domains which
harbor spammers. I wonder how the typical provider would handle:
- being told that their domains were refused service, and
- all the complaints from their legitimate customers who
get served off lists as a result.
The package you're looking for (if you want to do this) is tcpd;
earlier incarnations were known as tcp_wrapper.