Red Hat Enterprise Linux 5 Administration Unleashed

378CHAPTER 18Setting Up an Email Server with SendmailIf custom IPTables rules are being used, refer to Chapter 24, “Configuring a Firewall,” fordetails on how to allow these ports.If using a default security level in Red Hat Enterprise Linux, use the Security LevelConfiguration tool. Start it by selecting Administration, Security Level and Firewallfrom the System menu on the top panel of the desktop or by executing the systemconfig-securitylevelcommand. Enter the root password when prompted if running asa user. Click Add next to the Other ports table to add the appropriate ports.TIPIf setting up an internal email server, be sure to configure it to accept connectionsfrom IP addresses within your private network. If the email server is accessible overthe Internet and accepts email to be sent from any computer, it could be used byunauthorized users to send spam, or junk email, to people.SummaryIn most companies today, email is vital to internal communications. In many companies,it has replaced paper memos and bulletin board notices. This chapter described the pathan email takes after being sent. It then provides steps for setting up an email server onRed Hat Enterprise Linux using Sendmail. If used in conjunction with Dovecot, the sameserver used to send email can also support the IMAP and POP protocols for retrievingemail. Sendmail, POP, and IMAP can all be configured with an SSL certificate so emailsent and received is encrypted, making it harder to read if intercepted over the network.