---
name: "aliases"
section: "5"
platform: "linux"
package: "opensmtpd"
version: "7.9.0p0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/aliases"
---

# aliases(5)

aliases file for smtpd

## NAME

**aliases** – aliases file for smtpd

## DESCRIPTION

This manual page describes the format of the **aliases** file, as used by [smtpd(8)](/smtpd/8.md). An alias, in its simplest form, is used to assign an arbitrary name to an email address or a group of email addresses. This provides a convenient way to send mail. For example an alias could refer to all users of a group: email to that alias would be sent to all members of the group. Much more complex aliases can be defined however: an alias can refer to other aliases, be used to send mail to a file instead of another person, or to execute various commands.

Within the file, ‘#’ is a comment delimiter; anything placed after it is discarded. The file consists of key/value mappings of the form:

key: value1, value2, value3, ...

*key* is always folded to lowercase before alias lookups to ensure that there can be no ambiguity. The key is expanded to the corresponding values, which consist of one or more of the following:

- *user*

  A user on the host machine. The user must have a valid entry in the [passwd(5)](/passwd/5.md) database file.

- */path/to/file*

  Append messages to *file*, specified by its absolute pathname.

- \|*command*

  Pipe the message to *command* on its standard input. The command is run under the privileges of the daemon's unprivileged account.

- :*include*:*/path/to/file*

  Include any definitions in *file* as alias entries. The format of the file is identical to this one.

- *user-part@domain-part*

  An email address in RFC 5322 format. If an address extension is appended to the user-part, it is first compared for an exact match. It is then stripped so that an address such as user+ext@example.com will only use the part that precedes ‘+’ as a *key*.

- *error*:*code* *message*

  A status code and message to return. The code must be 3 digits, starting 4XX (TempFail) or 5XX (PermFail). The message must be present and can be freely chosen.

## FILES

- */etc/smtpd/aliases*

  Default **aliases** file.

## SEE ALSO

[smtpd.conf(5)](/smtpd.conf/5.md), [makemap(8)](/makemap/8.md), [newaliases(8)](/newaliases/8.md), [smtpd(8)](/smtpd/8.md)

## HISTORY

The **aliases** file format appeared in 4.0BSD.