Q I'm a member of a small church that has six computers networked in a peer-to-peer configuration, running Windows XP and 2000. The Internet connection to the local ISP is broadband (384K) We don't have a registered domain name, although we have five POP3 mailboxes on the ISP's server. I'd like to install a Linux server so that the user accounts, passwords and authentication could be managed by the server. I also want to implement file storage on the server.
I don't have a problem getting print and file-serving working, though - my question has to do with email. We have the five accounts that the paid and unpaid staff use, but we also have many volunteers who I'd like to set up so they could email each other on the local network. They wouldn't have to have Internet access. Microsoft Exchange could do this but we would need a registered domain name and the ISP would have to point the MX record at the domain. In addition, Exchange is expensive and overkill for us. Can Sendmail or Postfix be configured to obtain and send mail for the five ISP accounts from our local ISP, as well as handling internal mail without a registered domain name? Reading the manual strongly implies that this can be done, but how?
A Building a mail server is something that can be done very easily with Linux, and there is quite a range of different mail systems that can be mplemented. Sendmail is particularly complex and unless you're willing to learn the configuration file structure, using Postfix or Exim will make your life much easier. Both Postfix and Exim can be configured to accept mail for any domain, such as example.tld, which wouldn't be accessible via the Internet. Fetchmail can be implemented to download mail from the ISP and distribute it to the appropriate local users.
You'll also need to implement a POP3 service to enable clients to download messages from the mail server, and most distributions ship with pop3d, which is a basic POP3 server. For such a small system, a simple POP3 server is more than enough. However, if you want to expand and be able to handle users through a database, the Courier mail system has a courier-pop3 mail service that can function with MySQL. There are many cost-effective options available on the Internet, where you can provide access to mailboxes that you can have people send email to. However, providing email addresses that are only accessible between a small number of hosts will quickly lose its appeal and people will start to ask why they can't send email to the addresses from the outside world. Domains can be purchased extremely cheaply, and many domain providers offer unlimited email addresses.