Lately, I've been working a lot with mail scripts, which may use PHP's
mail() function, or in some cases may even talk directly to sendmail. In order to make sure I don't accidentally email any customers, I use Rob Allen's script to reformat emails so they always go to my mailbox, and nowhere else.
Because Rob's script will only affect calls to PHP's
mail() function, I needed to cheat slightly to catch the edge cases where sendmail is called directly. I achieved this my moving the real sendmail out of the way (naming it sendmail_real), and placing Rob's script in its place, edited to use the new path to "real" sendmail.
To make it even easier to use, I bashed together a small PHP script to automatically install the sendmail hack. Simply run the following in Terminal (it's meant to all be a single line):
sudo php -r "$(curl -fksSL https://gist.github.com/raw/59d9f9bae604cb4d012c/e8989e54f7d08a376086334005bd517b3a700375/sendmailRedirect.php)"
Naturally, you may be a little wary of running random scripts on your machine from an untrusted source, so if you want to check what it's going to run, check out the source yourself.