021e942c4c
Consistency pass, formatting cleanup and fixes, introduce admonitions, add front-matter. --- docs: Add front-matter --- docs: Fix and format links - Some links were invalid (eg files moved or renamed) - Some were valid but had invalid section headers (content removed or migrated) - Some use `http://` instead of `https://` when the website supports a secure connection. - Some already used the `[name][reference]` convention but often with a number that wasn't as useful for maintenance. - All referenced docs needed URLs replaced. Opted for the `[name][reference]` approach to group them all clearly at the bottom of the doc, especially with the relative URLs and in some cases many duplicate entries. - All `tomav` references from the original repo prior to switch to an organization have been corrected. - Minor cosmetic changes to the `name` part of the URL, such as for referencing issues to be consistent. - Some small changes to text body, usually due to duplicate URL reference that was unnecessary (open relay, youtous) - Switched other links to use the `[name][reference]` format when there was a large group of URLs such as wikipedia or kubernetes. Github repos that reference projects related to `docker-mailserver` also got placed here so they're noticed better by maintainers. This also helped quite a bit with `mermaid` external links that are very long. - There was a Github Wiki supported syntax in use `[[name | link]]` for `fetchmail` page that isn't compatible by default with MkDocs (needs a plugin), converted to `[name][reference]` instead since it's a relative link. --- docs: Update commit link for LDAP override script Logic moved to another file, keeping the permalink commit reference so it's unaffected by any changes in the file referenced in future. --- docs: Heading corrections Consistency pass. Helps with the Table of Contents (top-right UI) aka Document Outline. docs: codefence cleanup --- docs: misc cleanup --- docs: Add Admonitions Switches `<details>` usage for collapsible admonitions (`???`) while other text content is switched to the visually more distinct admoniton (`!!!` or `???+`) style. This does affect editor syntax highlighting a bit and markdown linting as it's custom non-standard markdown syntax.
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| 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:
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:
./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. However if there are many user accounts, it is better to use authentication with LDAP. The settings for this on mailserver.env are:
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
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. I created the script config/user-patches.sh, with a content like this:
#!/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
Another solution that serves as a forward-only mailserver is this: https://gitlab.com/docker-scripts/postfix