I had to hack it a bit to get it to work on Win32, and even then it behaved slightly strangely. I had to comment out:

if((getpwuid($>))[0] ne "root") {  # how is this handled on Microsoft 
+systems?
    print STDERR "You are ", (getpwuid($>))[0], " and $0 must be run a
+s root.\n";
    exit(1);
}
[download]

Then when I ran it I got this warning:

readline() on closed filehandle main::ALIASES at smtp.pl line 77.
[download]

Boy, smtp.pl didn't like that! I got tons of warnings:

Use of uninitialized value in exists at smtp.pl line 107, <GEN1> line 
+1.
Use of uninitialized value in chomp at smtp.pl line 100, <GEN1> line 1
+.
Use of uninitialized value in substitution (s///) at smtp.pl line 101,
+ <GEN1> l
[download]

But, it did send e-mail. Very nice little script.

Neat! I have to cringe as I read the source code though. There are only 19 commented lines out of 826! Also, it wasn't written with security in mind. For instance, if I have ftp access to an account on a machine running smtp.pl, I can execute arbitrary shell commands by uploading a file to my home directory named ".perlsmtp" containing the line "maildeliver = |/do/whatever".

Here's another thing that jumped out at me:

    open(CONFIG, $_[0]) or die "Could not open config file $_[0]\n";
[download]

Randal would call this "running with scissors". You should always, always, always specify a mode for open(). E.g.:

    open(CONFIG, "<$_[0]") or die "Could not open config file $_[0]\n"
+;
[download]

Otherwise you run the risk of a malicious user sneaking a value like "|rm -rf /home" into the filename. The above example isn't exploitable in the smtp script, mind you, but seeing that, I have to wonder what other bad habits might be lurking in the other 825 lines.

-Matt