I could supply a hard-wired From, and then pass the user's supplied From through the body of the message, but even that must pass through Mail::Mailer.

Surely I am just not seeing the simple solution. ;)

Some quick tests indicate that if Mail::Mailer really were using exec in a safe way, perl wouldn't care about $ENV{PATH}.

[sgifford@sghome sgifford]$ perl -T -e"exec('echo', 'OK')"
Insecure $ENV{PATH} while running with -T switch at -e line 1.
[sgifford@sghome sgifford]$ perl -T -e"exec('/bin/echo OK')"
Insecure $ENV{PATH} while running with -T switch at -e line 1.
[sgifford@sghome sgifford]$ perl -T -e"exec('/bin/echo', 'OK')"
OK
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What mailer are you using with Mail::Mailer, and what version? Can you find the relevant code that you think should be secure but Perl doesn't agree? Why is it a problem to untaint the from address to guarantee that it doesn't contain anything strange?

but it seems then, that it is telling me there is NO way to successfully pass a user-supplied From address to Mail::Mailer,

So what you're saying is that you're using taint mode without knowing how it works? All of the values in %ENV are tainted. If you don't know what that means, or how to get around it, read perlsec (it's a link you know).

MJD says "you can't just make shit up and expect the computer to know what you mean, retardo!"

I run a Win32 PPM repository for perl 5.6.x and 5.8.x -- I take requests (README).

** The third rule of perl club is a statement of fact: pod is sexy.

Mail::Mailer does use a piped open. From my version of Mail::Mailer (in MailTools 1.60) about line 226:

    # Fork and start a mailer
    (defined($exe) && open($self,"|-")) # (snip)
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I don't know enough about packages to know if this is a potentially harmful open call, but I can understand how the taint checking is complaining about the path.