Why use cron? This seems like something that would be handled by youre friendly neighborhood .forward file.
Either way you go, you could use a plain text file or one of perl's many persistent data modules to store which salesman should get the next e-mail. so the steps would be something like:

• read salesman's directory number from disk
• route STDIN to a file
• increment the directory number and write to disk

Actually, now that I look at it, I've done something quite similar to this...

akira:~$ cat .forward
|myproc.pl

akira:~$ cat myproc.pl
#! /usr/bin/perl -w
$fh = die "read that node more carefully!" # your to-do. load it from 
+a file.
open FH, ">>$fh" || die $!;
while (<STDIN>){
    print FH $_;
}
close FH;
# now alter whatever's in $fh, and save it to disk.
[download]

Make sense?