How to make fetchmail and sendmail work together

Hi, all:

I am installing RT on my home computer. My network connection is DSL,
no static IP address and domain name and port 25 is blocked by
ISP(Yahoo DSL).

I asked a question before in the list for the feasibility. Thanks for
Bob Goldstein, I am sure in theory it can work. He suggested me to use
the smtp server of the ISP for sending mails out; For receiving mails,
I can use fetchmail + sendmail so that fetchmail get all the mails
from the pop server of the ISP and deliver them to my local instance
of sendmail.

My questions are:

  1. How can I make fetchmail and sendmail work together? $fetchmail
    –smtphost localhost/25?
  2. The sender fields of the emails sent out through RT are something
    like general@my.fake.domain, how can I change that to
  3. After making fetchmail and sendmail working together, what type of
    changes shall I make so that the mailgateway can distinguish those
    emails and deliver them to different queues?

Thanks a lot!

Zhan Xu