fetchmail & pop3

[Sickchef]

Hello luau,

i am trying to setup my desktop redhat 7.0 to use fetchmail to retrieve
mail from various pop3 servers.  i have read the man page, and checked
out a couple of books to read more on it, but my question is how do i
set it up to sort mail or are we talking sendmail here for aliases like:

me at superduper.com  mail sent to --> /home/me/superduper
myotheraccount at superpooper.net ---> /home/me/superpooper

also, using a reader like elm, mutt, or pine, would i be able to send
email out with the aliase it was recieved from like:

recieved as --> me at superduper.com  --> sent as me at superduper.com from
the reader
&
recieved as -->myotheraccount at superpooper.com --> sent as
myotheraccount at superpooper.com

another note, nat is being used behind firewall, will this affect the
dns options in fetchmail, or should it be used at all<i don't think so>.

Please let me know if it doesn't make sense or i could try to rephrase
it.

Thanks is advance

Sickchef