firewall is able to establish direct network connections
firewall is able to establish direct network connections with hosts both on the private network and on the Internet. The smart host would accept mail from both hosts on the private network and the Internet, store them in local storage and then manage the retransmission of that mail to the correct host directly. Smart hosts are usually used when all other methods of delivery have failed. In the case of the organization with the private network, it would be perfectly reasonable to have the hosts attempt to deliver mail directly first, and if that fails then to send it to the smart host. This relieves the smart host of a lot of traffic because other hosts can directly send mail to other hosts on the private network. sendmail provides a simple method of configuring a smart host using the SMART_HOST feature; when implementing it in the Virtual Brewery configuration, we do exactly this. The relevant portions of our configuration that define the smart host are: define(`SMART_HOST’, `uucp-new:moria’) LOCAL_NET_CONFIG # This rule ensures that all local mail is delivered using the # smtp transport, everything else will go via the smart host. R$* < @ $* .$m. > $* $#smtp $@ $2.$m. $: $1 < @ $2.$m. > $3 The SMART_HOST macro allows you to specify the host that should relay all outgoing mail that you are unable to deliver directly, and the mail transport protocol to use to talk to it. In our configuration we are using the uucp-new transport to UUCP host moria. If we wanted to configure sendmail to use an SMTP-based Smart Host, we would instead use something like: define(`SMART_HOST’, `mail.isp.net’) We don’t need to specify SMTP as the transport, as it is the default. Can you guess what the LOCAL_NET_CONFIG macro and the rewrite rule might be doing? The LOCAL_NET_CONFIG macro allows you to add raw sendmail rewrite rules to your configuration that define what mail should stay within the local mail system. In our example, we’ve used a rule that matches any email address where the host belongs to our domain (.$m.) and rewrite it so that it is sent directly to the SMTP mailer. This ensures that any message for a host on our local domain is directed immediately to the SMTP mailer and forwarded to that host, rather than falling through to our smart host, which is the default treatment. Managing Unwanted or Unsolicited Mail (Spam) If you’ve subscribed to a mailing list, published your email address on a web site, or posted an article to UseNet, you will most likely have begun to receive unsolicited advertising email. It is commonplace now for people to scour the net in search of email addresses to add to mailing lists that they then sell to companies seeking to advertise their products. This sort of mass-mailing behavior is commonly called spamming. The Free On-line Dictionary of Computing offers a mail-specific definition of spam as:[1] 2. (A narrowing of sense 1, above) To indiscrimately send large amounts of unsolicited e-mail meant to promote a product or service. Spam in this sense is sort of like the electronic equivalent of junk mail sent to “Occupant.” In the 1990s, with the rise in commercial awareness of the net, there are actually scumbags who offer spamming as a “service” to companies wishing to advertise on the net. They do this by
Note: If you are looking for good and high quality web space to host and run your application check Lunarwebhost Linux Web Hosting services