[CentOS] Adding/Removing Headers with Sendmail

Hi,

I posted this query a few weeks ago but never received a response. I'm 
guessing that I didn't put things right, so here is another go.

The company that I work for currently has email addresses in the format 
of:-

firstname.surname.ext at example.com

Which we use for various marketing campaigns (therefore the .ext bit is
variable).

Currently we have this setup as distribution lists with exchange  so
that any email that goes to this addressess goes both to the sales
person and to a catch all mailbox which is then input into our systems.

I was wondering if it would be possible so that when an email is
received to this format of address it automatically determines where to
send it as follows

An email comes into joe.bloggs.sa... at example.com this then gets split so
that it is delivered to joe.blo... at example.com and also s... at example.com.

I think that i have figured out how to rewrite to the second address but
  how can I get it to send it to the new address as well.  I was hoping
there would be a way of doing this automatically so that we don't have
to setup these addresses for every new starter and they apply on a
global basis.

Hopefully that explains better what I am after.

Regards

Lee