[Techtalk] Securely transferring files using scripts

[jennyw]

Is there a way to securely transfer files using a script?  I'd like to 
write a backup script on my mail server to tar the messages and then send 
them to a backup server.  I'd like to use scp or something but don't want 
to pass a password.  Or, if a password needs to be used, is there a way to 
setup scp or something so that it would work with the shell being 
/dev/null?

Thanks!

Jen