[help] howto : setup a bsmtp (batch) smtp

[topcat]

Hello Group,

For some time i'm surfing for a 'how-to' for setting-up a bsmtp server. 
Without result.

 I just tried to search this mailinglist, but also no result.

This is the deal:
- i have a freebsd mail server with postfix running (pop/imap etc). 
Works great.
- now for some domains i would like this server to 'act' aswell as a 2nd 
(bsmtp) mail server. I know that you need to add a extra MX record to 
domain.
- i  installed /usr/port/mail/bsmtp.
- what i can't figure out is: how i can 'instruct' postfix to store the 
mail for some domains and try to send the (stored) mail each x minutes 
to the server it is intended too

Now, is it that hard to configure this? Or is it that simple (and i'm 
just to dumb to find out)?

Any help is appreciated, it drives me nuts :x

Many, many thanks in advance,

TC