mirror of
https://github.com/docker-mailserver/docker-mailserver.git
synced 2024-01-19 02:48:50 +00:00
106 lines
3.9 KiB
Markdown
106 lines
3.9 KiB
Markdown
---
|
|
title: 'Use Cases | Forward-Only Mailserver with LDAP'
|
|
---
|
|
|
|
## Building a Forward-Only Mailserver
|
|
|
|
A **forward-only** mailserver does not have any local mailboxes. Instead, it has only aliases that forward emails to external email accounts (for example to a gmail account). You can also send email from the localhost (the computer where the mailserver is installed), using as sender any of the alias addresses.
|
|
|
|
The important settings for this setup (on `mailserver.env`) are these:
|
|
|
|
```env
|
|
PERMIT_DOCKER=host
|
|
ENABLE_POP3=
|
|
ENABLE_CLAMAV=0
|
|
SMTP_ONLY=1
|
|
ENABLE_SPAMASSASSIN=0
|
|
ENABLE_FETCHMAIL=0
|
|
```
|
|
|
|
Since there are no local mailboxes, we use `SMTP_ONLY=1` to disable `dovecot`. We disable as well the other services that are related to local mailboxes (`POP3`, `ClamAV`, `SpamAssassin`, etc.)
|
|
|
|
We can create aliases with `./setup.sh`, like this:
|
|
|
|
```sh
|
|
./setup.sh alias add <alias-address> <external-email-account>
|
|
```
|
|
|
|
## Authenticating with LDAP
|
|
|
|
If you want to send emails from outside the mailserver you have to authenticate somehow (with a username and password). One way of doing it is described in [this discussion][github-issue-1247]. However if there are many user accounts, it is better to use authentication with LDAP. The settings for this on `mailserver.env` are:
|
|
|
|
```env
|
|
ENABLE_LDAP=1
|
|
LDAP_START_TLS=yes
|
|
LDAP_SERVER_HOST=ldap.example.org
|
|
LDAP_SEARCH_BASE=ou=users,dc=example,dc=org
|
|
LDAP_BIND_DN=cn=mailserver,dc=example,dc=org
|
|
LDAP_BIND_PW=pass1234
|
|
|
|
ENABLE_SASLAUTHD=1
|
|
SASLAUTHD_MECHANISMS=ldap
|
|
SASLAUTHD_LDAP_SERVER=ldap.example.org
|
|
SASLAUTHD_LDAP_SSL=0
|
|
SASLAUTHD_LDAP_START_TLS=yes
|
|
SASLAUTHD_LDAP_BIND_DN=cn=mailserver,dc=example,dc=org
|
|
SASLAUTHD_LDAP_PASSWORD=pass1234
|
|
SASLAUTHD_LDAP_SEARCH_BASE=ou=users,dc=example,dc=org
|
|
SASLAUTHD_LDAP_FILTER=(&(uid=%U)(objectClass=inetOrgPerson))
|
|
```
|
|
|
|
My LDAP data structure is very basic, containing only the username, password, and the external email address where to forward emails for this user. An entry looks like this
|
|
|
|
```properties
|
|
add uid=username,ou=users,dc=example,dc=org
|
|
uid: username
|
|
objectClass: inetOrgPerson
|
|
sn: username
|
|
cn: username
|
|
userPassword: {SSHA}abcdefghi123456789
|
|
email: real-email-address@external-domain.com
|
|
```
|
|
|
|
This structure is different from what is expected/assumed from the configuration scripts of the mailserver, so it doesn't work just by using the `LDAP_QUERY_FILTER_...` settings. Instead, I had to do [custom configuration][github-file-readme-patches]. I created the script `config/user-patches.sh`, with a content like this:
|
|
|
|
```bash
|
|
#!/bin/bash
|
|
|
|
rm -f /etc/postfix/{ldap-groups.cf,ldap-domains.cf}
|
|
|
|
postconf \
|
|
"virtual_mailbox_domains = /etc/postfix/vhost" \
|
|
"virtual_alias_maps = ldap:/etc/postfix/ldap-aliases.cf texthash:/etc/postfix/virtual" \
|
|
"smtpd_sender_login_maps = ldap:/etc/postfix/ldap-users.cf"
|
|
|
|
sed -i /etc/postfix/ldap-users.cf \
|
|
-e '/query_filter/d' \
|
|
-e '/result_attribute/d' \
|
|
-e '/result_format/d'
|
|
cat <<EOF >> /etc/postfix/ldap-users.cf
|
|
query_filter = (uid=%u)
|
|
result_attribute = uid
|
|
result_format = %s@example.org
|
|
EOF
|
|
|
|
sed -i /etc/postfix/ldap-aliases.cf \
|
|
-e '/domain/d' \
|
|
-e '/query_filter/d' \
|
|
-e '/result_attribute/d'
|
|
cat <<EOF >> /etc/postfix/ldap-aliases.cf
|
|
domain = example.org
|
|
query_filter = (uid=%u)
|
|
result_attribute = mail
|
|
EOF
|
|
|
|
postfix reload
|
|
```
|
|
|
|
You see that besides `query_filter`, I had to customize as well `result_attribute` and `result_format`.
|
|
|
|
For more details about using LDAP see: [LDAP managed mail server with Postfix and Dovecot for multiple domains](https://www.vennedey.net/resources/2-LDAP-managed-mail-server-with-Postfix-and-Dovecot-for-multiple-domains)
|
|
|
|
Another solution that serves as a forward-only mailserver is this: https://gitlab.com/docker-scripts/postfix
|
|
|
|
[github-file-readme-patches]: https://github.com/docker-mailserver/docker-mailserver/blob/master/README.md#custom-user-changes--patches
|
|
[github-issue-1247]: https://github.com/docker-mailserver/docker-mailserver/issues/1247
|