[CentOS] Security advice, please

[John Doe]

> Then, I want to read from my own IMAP server when I'm away from home.  Is 
> there a better way than opening port 143?

The easiest would be if you had a fixed external IP and only allow it; but I guess that won't be the case.
Maybe using an other port than 143?  But I don't think that would fool port scanners.
Or you could firewall everything and try "port knocking" to open it on demand and let you go through...

JD