Re: filtering duplicates - a gotcha

David already answered the real questions in your post, but I'll point
out one inefficiency:

gary(_at_)Intrepid(_dot_)Com (Gary Funck) writes:
> :0
> * ? formail -D 10000 ~/.dup_id_cache
> dup-mail
The presence of the tilde in that shell condition forces procmail to use
a shell when it evaluates it, instead of executing formail directly.  If
instead you used $HOME, procmail could be able to do the expansion itself,
saving a process:

        :0
        * ? formail -D 10000 $HOME/.dup_id_cache
        dup-mail


Philip Guenther