A lot of small businesses think that to have their own domain and email address is an expensive proposition, but with a lot of the web packages that are available now it is possible to do it quite cheaply. The only thing you need is a machine to act as a server at your home or office and then any free unix based server software can then be loaded onto that machine and it will then be able to handle all the functions that are mentioned in the 'Server installation and configuration' section. Some functions will be easier to set up if a static IP address is used for you internet connection, but there are ways to get things running if this is not easy to do. If you have a mobile phone that allows email or calendar access then you will now be able to connect to your server from anywhere in the world with it.
If you decide instead to go with an online service, like Google Apps or Outlook.com, then your domain can be configured to point to these services and any current email data can be transferred from the current server that you are using, or the data can be copied from your email client, if you collect your emails with the POP protocol.