[rt-users] Simple Questions

[RT2 Troubles]

When configuring the rt2/etc/config.pm file I am stumped by a few options:

$CorrespondAddress
$CommentAddress
- I can't seem to find documentation for this, but I may just need an example 
here. Like if my server is rt.foo.com what would these be set to?

$TicketBaseURI
- Linking tickets remotely? Privacy is an issue for the RT2 server we are 
setting up, and this feature appears to 'share' ticket info. Can someone 
explain this feature?

Also, in the admin screen, when adding a user, it asks for the unix login. 
What  would that be used for?

Thanks again for all the assistance, this list is very informative!