Linux Network Administrator's Guide, Second Edition

Some Useful sendmail Configurations

There are myriad possible sendmail configurations. In this space we’ll illustrate just a few important types of configuration that will be useful in many sendmail installations.

Trusting Users to Set the From: Field

It is sometimes useful to overwrite the From: field of an outgoing mail message. Let’s say you have a web-based program that generates email. Normally the mail message would appear to come from the user who owned the web server process. We might want to specify some other source address so that the mail appears to have originated from some other user or address on that machine. sendmail provides a means of specifying which systems users are to be entrusted with the ability to do this.

The use_ct_file feature enables the specification and use of a file that lists the names of trusted users. By default, a small number of system users are trusted by sendmail (root, for example). The default filename for this feature is /etc/mail/trusted-users in systems exploiting the /etc/mail/ configuration directory and /etc/sendmail.ct in those that don’t. You can specify the name and location of the file by overriding the confCT_FILE definition.

Add FEATURE(use_ct_file) to your sendmail.mc file to enable the feature.

Managing Mail Aliases

Mail aliases are a powerful feature that enable mail to be directed to mailboxes that are alternate names for users or processes on a destination host. For example, it is common practice to have feedback or comments ...