Email services on your Virtual Private Server are managed by the sendmail program, with various other Email tools providing extended capabilities.

sendmail is a configurable, robust SMTP server that processes all incoming and outgoing messages on your VPS. Any VPS Users can send and receive e-mail messages with sendmail, although in order to check or send E-mail from a remote client (such as Outlook or Eudora), the user must also have POP or IMAP permissions.

Configuring sendmail

The sendmail program on VPS runs as a daemon (a program that is always running). When you make changes to any of the sendmail configurations, you must restart sendmail to load the new settings into the daemon. To restart sendmail, the root user must run the following command from the VPS shell.

# restart_sendmail

You can also change to the /etc/mail directory and use make restart. The make command can also take stop or start to respectively stop or start the sendmail daemon.

Domains, aliases, and forwards

When an E-mail message arrives on your VPS, sendmail checks the incoming domain and determines if it is either a local domain, or an authorized relay domain. In addition to the VPS hostname (or primary domain), which is always considered a local domain, you can have any number of local domains on your server. In order to be considered local, you must have the domain listed in the /etc/mail/local-host-names file on your server. Once a domain is determined to be local, sendmail checks the virtusertable and then the aliases files to determine if there is any special delivery conditions for the recipient address.

Once an E-mail recipient has been checked against the virtusertable for domain based delivery, the domain name of the recipient is ignored by sendmail. The username, without the domain, is then checked against the aliases, and finally delivered to the correct local user's mailbox.

Your VPS can also be configured to relay E-mail messages from authorized domains. This allows you to use your VPS as a secondary mail server. When an E-mail message arrives with a recipient domain that is listed in the /etc/mail/relay-domains file, sendmail will try to deliver the message to the primary server. If the primary server is unable to accept the mail, sendmail will hold the messages in a special queue, and will deliver them to the primary mail server once the primary server is online again. This feature is especially useful to companies using Exchange servers, or who have limited network access to their primary mail server.

Mail Filtering and spam prevention

In addition to recipient based mail routing, sendmail can be configured to filter or route messages based on other elements of the message. The easiest way to do this is with Procmail, an easy to configure mail filtering add-on. You can also configure sendmail itself for filtering using the M4 macro set.

While there are many possible reasons to filter mail, one of the most common uses is to prevent SPAM (or UCE).

Other Popular E-mail Tools

There are a number of additional e-mail tools that you can configure for your VPS. Some of the more popular ones include E-mail list Managers, E-mail message encryption, and E-mail Automatic Reply.

Using Remote Mail Clients

For VPS users with Mail permissions, POP and IMAP compatible remote mail clients can be used to download and send E-mail messages. For more information, see Configuring E-mail Clients.

Please note: the information on this page applies to ITS web hosting plans. It may or may not apply to other environments. If you are looking for a feature described here, or better support from your hosting provider, please consider hosting your site with ITS!

1555 N Naperville/Wheaton Road, Suite 107
Naperville, IL 60563
phone 630.420.2550
fax 630.420.2771