Question: How do I enable DNS (bind) in my Mac Mini

The DNS service comes disabled in OS X Standard. To enable, follow the steps described in the article How to Enable Bind.
The steps follow:
1) sudo -s
2) Edit /etc/named.conf to comment the following line:
//include "/etc/rndc.key";
3) In the same file, modify the controls section to look like this:
controls {
inet 127.0.0.1 port 54 allow {any;};
//keys { "rndc-key"; }; };
};
4)Edit the file /System/Library/LaunchDaemons/org.isc.named.plis, and change the like under <key>Disabled</key> from <true/> to <false/>
5)To make bind listen to the public IP, edit /etc/named.conf to adding this section inside the options section:
listen-on {
my-ip-here;
127.0.0.1;
};
6) Launch named:
cd /System/Library/LaunchDaemons
launchctl stop org.isc.named
launchctl unload org.isc.named.plist
launchctl load org.isc.named.plist
launchctl start org.isc.named

Question: How do I enable SMTP in my Mac Mini

The mail service comes disabled in OS X Standard. To enable, follow the steps described in the article How to Enable Postfix.
After that, to make SMTP listen to requests from the Internet, edit the file /etc/postfix/main.cf, and change the line "inet_interfaces = localhost" to "inet_interfaces = all".
Restart the service with "service org.postfix.master stop" and "service org.postfix.master start"

Question: How do I enable IMAP and POP3 in my Mac Mini

Easy way: For $9.99, let PostFix Enabler do it for you. Get it here
Otherwise, follow these steps:
1) Install XCode Tools from the OS X Installation CD/DVD
2) Install DarwinPorts. Download it here
3) Install IMap-uw, with the following command:
sudo port install imap-uw
4) The following commands will set the service to start automatically:
cd /opt/local/var/db/dports/sources/
cd rsync.rsync.darwinports.org_dpupdate_dports/mail/imap-uw/files
sudo cp etc-pam.d-imap /etc/pam.d/imap
sudo cp etc-xinetd.d-imap /etc/xinetd.d/imap
sudo cp etc-xinetd.d-imaps /etc/xinetd.d/imaps
5) Edit the files /etc/xinetd.d/imap and /etc/xinetd.d/imap. Replace __PREFIX with /opt/local
6) Edit the file /etc/inetd.conf, and modify the line for pop3, to:
pop3  stream  tcp  nowait   root   /usr/libexec/tcpd   /opt/local/libexec/ipop3d
7) Restart the service with:
sudo kill -HUP `cat /var/run/xinetd.pid`