---
name: "courierpop3d"
section: "8"
platform: "linux"
package: "courier-pop"
version: "1.4.1-3+deb13u2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/courierpop3d"
---

# courierpop3d(8)

The Courier POP3 server

## NAME

courierpop3d - The Courier POP3 server

## SYNOPSIS

**/usr/sbin/couriertcpd** {-nodnslookup} {-stderr=syslog} {110} {/usr/lib/courier/courier/courierpop3login} \[*modules*...\] {/usr/lib/courier/courier/courierpop3d} {./Maildir}

## DESCRIPTION

This is a simple POP3 server for Maildirs.

**Note**\

The **couriertcpd**, **courierpop3login**, and **courierpop3d** modules may be installed elsewhere than indicated here.

**courierpop3login** is usually started by **couriertcpd**. It already expects that a POP3 client is connected to standard input and output, presumably via a network socket. **courierpop3login** reads the POP3 userid and password, then runs the authentication modules. The remaining arguments are passed along as arguments to modules.

modules is one or more authentication modules (see the [**authlib**(7)](/authlib/7.md)\[1\] manual page).

Each authentication modules runs the program specified by its first argument, allowing the authentication modules to be chained. The last program in the chain is **courierpop3d** , which provides the actual POP3 service. In accordance with the authentication protocol, as described in [**authlib**(7)](/authlib/7.md)\[1\] **courierpop3d** reads file descriptor 3 to see if the userid/password has been succesfully validated. If not, **courierpop3d** terminates.

Otherwise, **courierpop3d** expects to be already running under the appropriate user and group id, with its current directory set to the account's home directory.

The first order of business is to find the account's Maildir. If the environment variable **MAILDIR** is set, that's where we go. That should be the pathname to the account's Maildir. The environment variable **MAILDIR** may be set by the authentication module. If **MAILDIR** is not set, **courierpop3d** uses its first argument. Usually, the default maildir is $HOME/Maildir, therefore the first argument to **courierpop3d** is "./Maildir".

## SEE ALSO

[**authlib**(7)](/authlib/7.md)\[1\], [**userdb**(8)](/userdb/8.md)\[2\].

## AUTHOR

**Sam Varshavchik**

Author

## NOTES

- 1\.

  [**authlib**(7)](/authlib/7.md)

  http://www.courier-mta.org/authlib.html

- 2\.

  [**userdb**(8)](/userdb/8.md)

  http://www.courier-mta.org/userdb.html