Quoting Chris Mulcahy <tclug at cmulcahy.com>:

<snip>
>
> Grey listing is a good thing.  The "Hello?  Are you a human?"
> confirmation messages are EVIL!
>
> Chris
>

Agreed. At a previous position of mine my VP decided to try one of 
those foul things because he thought we were having spam problems, if 
only he knew how much spam I had kept out of his In Box. That little 
piece of crapware resulted in several nasty grams to postmaster@, which 
I had the privilege of reading. Josh