How to Access DB and Mail from outside network

[kendel]

I followed the first 3 pages of The Perfect Server – Ubuntu 12.04 LTS (Apache2, BIND, Dovecot, ISPConfig 3) which was basically just installation and configuration (easy enough)... I may have substituted some of the configuration of the network file and host file for the second part of the installation which was Multi Server setup.

I basically finished off with that. My question is, as I was doing this I noticed there wasn't a mail client installed. Can I after finishing everything and getting it working, still install a mail client on the mail server for access. How do I do them (if you can point me to a guide, I really don't mind reading)?