MTA Configuration

When you run the Mail Transfer Agent component in YaST, you are configuring Postfix and Fetchmail. Postfix has been the standard MTA in SUSE Linux since version 8.1. Earlier SUSE Linux versions used the still more widely used Sendmail MTA. Sendmail is notoriously difficult to configure, and Postfix is not. Postfix also handles more traffic faster than Sendmail. Thus, it is not hard to see why the SUSE developers made the switch.

For users, however, there is little difference, because YaST controls the configuration. Creating your own configuration file manually is possible, but can be overwritten with every update because YaST always runs Suseconfig after installing new packages.

In this section, we will deal with the extra screens available in the YaST MTA Wizard. Basic users should stick to the defaults for these settings, but if you want to fine-tune your mail operations, read on.

Masquerading

Suppose you have a user with a different mail account, and all his mail should come from that account. Use the Local User dialog box to specify the user and the address that should appear in the From line in his email messages.

Authentication

Some ISPs require a password to send mail using its SMTP servers. If yours is one of them, use this dialog box to identify the server, your username, and your password. If you do not have this information, you may need to require it from your ISP's technical support channels.

Remote SMTP Connections

Check the Accept Remote SMTP Connections box if this system is a mail server. This will allow your users to send mail through this system.

Incoming Mail Protocols

As noted earlier, there are two primary ways of receiving mail: POP3 and IMAP. Other protocols can be used to receive/download mail, and they are listed in the drop-down menu. By default, Postfix contacts the server and determines what protocol it uses automatically. The other protocols are the following:

• POP2 Possibly still present on some mail servers, this version of the Post Office Protocol is really old.

• APOP, KPOP More secure authentication than ordinary POP.

  Note

  Though it is one of the most used services on the network, and has been for quite some time, email remains one of the most insecure services as well. Any security features you can add to the service including more secure clients help head off problems before they occur.

  
  

• SDPS The special POP3-compliant protocol used by Demon Internet, an ISP in the United Kingdom.

• ETRN Short for Extended Turn, an extension to the SMTP mail delivery protocol that allows an SMTP server to request from another SMTP server any email messages it has for a specific domain. ETRN typically is used to retrieve email messages from a mail server that does not have a dedicated connection to the Internet (from webopedia.com).

• ODMR On Demand Mail Relay.

If your ISP uses one of these different protocols, they should tell you about it. Otherwise, Fetchmail's automatic detection should work fine.

Delivery Mode

The default here is Directly. To use the Cyrus IMAP server included with SUSE Linux, choose this option from the drop-down menu. To use Procmail to have more control over your mail delivery, choose this option. See the section "Fighting Spam and Viruses" in this chapter for more information.

Aliases

Aliases enable you to specify unlimited valid email addresses for your local account (but not mail received through your ISP) without having to create a real user with a login. Mail addressed to <alias>@<yourdomainname> (or IP address) is forwarded to one real user account.

Opening the Aliases dialog box displays dozens of default aliases along with the real accounts that the mail to those aliases forwards to. Add to the list and edit or remove existing aliases by selecting the alias you want to work with, and click the appropriate button.

Virtual Domains

Aliases let you change the username part of an email address. Virtual domains (also called virtual hosting) allow you to change the domain part of the address as well.

Read more about this in Chapter 26, "Managing Your Apache Web Server."