O.T. milter-null experiences, whitelists?

[Ken A]

Anyone have any experience with snertsoft's milter-null?
I've installed it, and it seems to identify backscatter quite well.

I'm a bit concerned about roaming users not getting failed delivery 
notifications if they send out through an outside smtp server though.

Any thoughts on this, or whitelists of stupid autoresponders or CR 
systems that send from <>? Earthlink's C/R Anti-spam system used to do this.

Thanks,
Ken A.
Pacific.Net