Question : Exim, Cached DNS for MX records, Spam, Postini

Our server is a LAMP, Cpanel, Exim

We have too many instances of emails that arrive directly to the server IP address without "obeying" the MX record pointer which points to Postini (so that spam can be filtered there).

Does anyone know of an exim "plug-in"  (not sure what to call it;   "rule"? )  to use so that spam can be redirected to the postini server from within our server rather than just at the MX record level?

To say it another way:
right now many/most emails are in fact following the MX record pointer and being processed through Postini.
This is at a level at the "outskirts" of the server such that when it returns directly to the server IP address, it then goes into exim for distribution to the proper mailbox.
However, some spam senders are sending directly to the IP address which circumvents the MX record and thus postini never gets a chance to filter.
I'm wondering if there's a way to put a splitter/interruptor in from WITHIN exim some way to send to postini and then postini returns it for correct email distribution?

hope all that makes sense.
thanks

Answer : Exim, Cached DNS for MX records, Spam, Postini

All LEGIT email should be sent to your MX record. Spammers are the ones abusing the fact that they can send directly to the mail server. Once I made the changes above normal email continued to flow correctly I just wan't getting the Spam anymore.