Today, email is a very important part of many people's life, so it's no surprise Debian lets you configure your mail system right as a part of the installation process. The standard mail transport agent in Debian is exim4, which is relatively small, flexible, and easy to learn. You may ask if this is needed even if your computer is not connected to any network. The short answer is: Yes. The longer explanation: Some system utilities (like cron, quota, aide, …) may send you important notices via email. So on the first screen you will be presented with several common mail scenarios. Choose the one that most closely resembles your needs: internet site Your system is connected to a network and your mail is sent and received directly using SMTP. On the following screens you will be asked a few basic questions, like your machine's mail name, or a list of domains for which you accept or relay mail. mail sent by smarthost In this scenario is your outgoing mail forwarded to another machine, called a smarthost, which does the actual job for you. Smarthost also usually stores incoming mail addressed to your computer, so you don't need to be permanently online. That also means you have to download your mail from the smarthost via programs like fetchmail. This option is suitable for dial-up users. local delivery only Your system is not on a network and mail is sent or received only between local users. Even if you don't plan to send any messages, this option is highly recommended, because some system utilities may send you various alerts from time to time (e.g. beloved Disk quota exceeded). This option is also convenient for new users, because it doesn't ask any further questions. no configuration at this time Choose this if you are absolutely convinced you know what you are doing. This will leave you with an unconfigured mail system — until you configure it, you won't be able to send or receive any mail and you may miss some important messages from your system utilities. If none of these scenarios suits your needs, or if you need a finer setup, you will need to edit configuration files under the /etc/exim4 directory after the installation is complete. More information about exim4 may be found under /usr/share/doc/exim4.