Forwarding email ports

[Michael_google gmail_Gersten]

I read through the january archives on email ports, specifically 465,
587, and 995.

First, are these the ports needed to support standard secure email
(SMTP and PoP)?

Second, why were there three of them for two protocols? Did I
misunderstand something?

Third, what are the implications -- both security, and legal -- if I
open these on my machine. I'm thinking in particular, that:
1. If only one exit node is outputting these ports, it becomes an
obvious snoop target -- how does that affect security?
2. If I'm forwarding email, am I likely to find my site "blacklisted" somewhere?
3. Am I likely to get some sort of "Cease and desist" letter, or other
legal hassle, for this?
4. Since my machine has about 22K/s bandwidth, how likely is it that I
will be badly backlogged / overtargetted?