/etc/aliases: Explanation & Insights

Defines email aliases

In a Linux or Unix-based operating system, /etc/aliases is a file that contains a list of email aliases, which are used to redirect email messages from one user or address to another. The /etc/aliases file is read by the mail transfer agent (MTA) on the system and allows for the creation of custom email addresses without having to create a new user account.

Here are some examples of how the /etc/aliases file can be used:

Redirecting email to another user:

root: user@example.com

In this example, all email messages that would normally be sent to the root user will be redirected to the user@example.com address instead.

Creating a mailing list:

sales: user1@example.com, user2@example.com, user3@example.com

In this example, any email messages sent to the sales address will be forwarded to the three listed email addresses.

Creating a custom email address:

support: user@example.com

In this example, any email messages sent to the support address will be forwarded to the user@example.com address.

Creating an email filter:

junk: /dev/null

In this example, any email messages sent to the junk address will be deleted without being delivered to any user.

It's important to note that after making changes to the /etc/aliases file, the newaliases command must be run in order for the changes to take effect. This command rebuilds the alias database used by the MTA.