I wanted to setup a simple cron job that would send an output of a simple file to a simple e-mail address.. something like..

tail -10 whatever.txt | mail -s "here's whatever" whomever@spamme.com

No, of course that's too easy.. when you use a picky postfix server that rejects addresses like, say root@hostname as invalid..

Back to the drawing board... Write a complex perl script or see if there's any way of doing this with a shell one-liner.. and this is where postfix compatibility with sendmail really pays off..

tail -10 whatever.txt | sendmail -f dumbass@localhost.com -s "here's whatever" whomever@spamme.com

Voila.. Reply-to is set, postifx is happy.. a one liner after all.

I'm a bit annoyed that I couldn't find a way of doing this with mail though.. Google failed me..

(yes, save your "reconfigure postifx" comments.. that's unnecessary and too much work)