Briefly, 


The Bohr--planetary model doesn't really address these issues.


Bohr, a genius, just asserted that the phenomena at the atomic level were a combination of stationarity while being in an orbit, and discrete quantum jumps between the orbits.  It was a postulate that yielded some agreement with experiment and was very helpful for the future development of quantum mechanics solely because it got people to think about stationarity and discreteness. 

2 It is totally useless for discussing chemical bonds.   You are quite right to be uncomfortable with it.

3  It would be stretching a point, but you could see the Quantum Mechanics of Heisenberg and Schroedinger as the only way to salvage the planetary model of Bohr, by finally coming up with an explanation for the stationarity of an electron's state around (but no longer considered as « orbiting ») the nucleus and an explanation for discrete jumps as a response to perturbations from outside.  But this required seeing the electron more as a wave and hence not having any definite location along the orbit.

Why don't electrons crash into the nuclei they "orbit"?
I'm trying to setup Exim on a fresh CentOS install so that it will receive mail for a collection of given addresses, and forward the mail respectively to another address. For example, receiving mail from me@example.com would be forwarded to me@gmail.com.

I figure this should be fairly straight forward... I had this working before with Sendmail, using the virtusertable - is there something similar I can do with Exim?

I'd also like to be able to send mail, but only for mail being sent from the local machine (i.e., from applications running on the server) - I don't need/want a publicly available SMTP server.

Are there any other settings I should bear in mind to make sure the mail server is secure? (i.e., prevent relaying) I'm assuming that it will be secure out of the box.

Thanks.
