Large-Scale Mail with Postfix, OpenLDAP and Courier
Now that slapd is configured, it's time to start adding data to the LDAP directory. We use the command-line tools that come with OpenLDAP and create LDIF files to modify the directory.
The first step is to create a base tree structure with our root node, the hosting organization and an entry for the rootdn. Create a file called base.ldif with the following contents:
dn: dc=myhosting, dc=example objectClass: top dn: cn=Manager, dc=myhosting, dc=example objectClass: top objectClass: organizationalRole cn: Manager dn: o=hosting, dc=myhosting, dc=example objectClass: top objectClass: organization o: hosting
Now use ldapadd, binding as the root account, to add this LDIF:
ldapadd -x -D "cn=Manager,dc=myhosting,dc=example" \ -w secret -f base.ldif
Domains can now be added under the hosting tree. Each domain needs to have postmaster and abuse entries at minimum. To make a tree for domain1.example, create a file called domain1.example.ldif with the following contents:
dn: o=domain1.example, o=hosting, dc=myhosting, dc=example objectClass: top objectClass: organization o: domain1.example dn: cn=postmaster, o=domain1.example, o=hosting, dc=myhosting, dc=example objectClass: top objectClass: organizationalRole objectClass: CourierMailAlias cn: postmaster mail: maildrop: postmaster dn: firstname.lastname@example.org, o=domain1.example, o=hosting, dc=myhosting, dc=example objectClass: top objectClass: CourierMailAlias mail: maildrop: abuse
Notice that the maildrop attributes are local e-mail accounts and will forward to the postmaster and abuse accounts in /etc/aliases. There are no accounts in the postmaster role, so only the root account can create accounts at the moment. Add this domain with the following command:
ldapadd -x -D "cn=Manager,dc=myhosting,dc=example" \ -w secret -f domain1.example.ldif
Now, let's add an account with an e-mail <email@example.com>. Let's also grant this account postmaster privileges for domain1.example. Create a user1.domain1.example.ldif with the following contents:
dn: firstname.lastname@example.org, o=domain1.example, o=hosting, dc=myhosting, dc=example objectClass: top objectClass: CourierMailAccount mail: homeDirectory: /home/vmail/domains uidNumber: 101 gidNumber: 101 mailbox: domain1.example/user1 dn: cn=postmaster, o=domain1.example, o=hosting, dc=myhosting, dc=example changetype: modify add: roleOccupant roleOccupant: email@example.com, o=domain1.example, o=hosting, dc=myhosting, dc=example
The first section adds a new entry for the account. The home directory and mailbox point to the physical mailbox on the filesystem. The uidNumber and gidNumber attributes are required but not used, so they are filled in with dummy values of 101. The second section modifies the postmaster entry by adding a roleOccupant attribute with the DN of firstname.lastname@example.org. Let's create this account:
ldapadd -x -D "cn=Manager,dc=myhosting,dc=example" \ -w secret -f user1.domain1.example.ldifThe account does not have a password yet, so even though it has been granted postmaster privileges, it cannot be authenticated. Use the ldappasswd command to set the initial password to user1:
ldappasswd -x -D "$DN" -w $PW -s user1 \ "email@example.com, o=domain1.example, o=hosting, dc=myhosting, dc=example"Other domains and accounts can be added with similar LDIF files. Creating LDIF files by hand can be cumbersome and error-prone. We discuss alternatives for administration later.
We cover only the sections of Postfix that pertain to the mail hosting. To deal with other parts of Postfix setup, please visit the Postfix web page.
Download the Postfix source and untar it. You need to rebuild the Postfix Makefiles to be aware of LDAP and link against it. To do this, execute the following command:
make makefiles CCARGS="-I/usr/local/include -DHAS_LDAP" AUXLIBS="-L/usr/local/lib -lldap -L/usr/local/lib -llber"
At this point, follow the normal Postfix compiling and installing instructions as documented in its INSTALL and LDAP_README files.
While configuring Postfix for this task, we are mostly concerned with /etc/postfix/main.cf. For most of the Postfix configuration, you will configure in a way that makes the most sense for your site, and you can follow the documentation contained in the Postfix source or on the Postfix web site. Here, we talk about the settings that are affected by this setup. If any of the configuration examples shown below aren't explicitly attributed to a specific file, assume they can be found in main.cf.
The transport table maps domains to message delivery transports (as specified in /etc/postfix/master.cf) and/or relay hosts. For our virtual domains, we want to map them to the virtual delivery agent that comes with Postfix. A transport table could look something like this:
domain1.example virtual: domain2.example virtual:
After making your transport table in plain text, you need to make it into a binary DB file using postmap (see man postmap). At this point, tell Postfix that there is a transport table and where to find it. You also need to let Postfix know that we accept mail for those domains. This is done through the transport_maps and mydestination directives:
transport_maps = hash:/etc/postfix/transport mydestination = $myhostname, localhost.$mydomain, $mydomain, $transport_mapsYou can define multiple LDAP sources easily. LDAP source parameters are documented in README_FILES/LDAP_README in the Postfix source. The parameter names follow the pattern of <ldapsource>_parameter. The LDAP source name is defined by use. In main.cf, you'll need one LDAP source definition per each lookup.
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