Installing DBMail with Postfix
This document will help you set up the Postfix mailer to deliver mail to a DBMail instance.
Prerequisites
Before attempting the configuration steps suggested here, you should already have the following prerequisites in place:
- A DBMail installation
- A Postfix installation
Packages may be available from your OS vendor, or your can download the source yourself from a postfix.org mirror.
It is also recommended that you read through this entire page before trying any of the steps given here.
This document will assume that your Postfix configuration files are located at /etc/postfix/
Make sure you've read and executed the steps from the INSTALL file before configuring your MTA. You'll want to be sure that DBMail is ready to deliver mails before sending your messages to it!
Delivery Methods
You must choose from DBMail's two supported delivery methods: LMTP using dbmail-lmtpd and a command line pipe using dbmail-deliver.
- dbmail-lmtp features network delivery, better performance , reliable performance and bounce handling. It uses a long-running dedicated connection to the authentication and storage database.
- dbmail-deliver uses piped delivery through a short-lived command line utility. A new database connection is created and used for each incoming email, reducing performance compared to LMTP.
Postfix interfaces directly with MySQL or PostgreSQL to check for aliases before sending mail to dbmail (pipe or LMTP).
To use MySQL or PostgreSQL with Postfix, first install the postfix-mysql or postfix-pgsql packages.
Using LMTP Delivery
in /etc/postfix/master.cf add:
dbmail-lmtp unix - - n - - lmtp
If you want verbose output in the mail log, add -v to lmtp, like this:
dbmail-lmtp unix - - n - - lmtp -v
Note that this setting will result in a LOT of extra output in your logs.
If one or more destinations in your mydestination list are not DNS-resolvable, DNS lookups must be disabled for the dbmail-lmtp daemon, like this:
dbmail-lmtp unix - - n - - lmtp
-o disable_dns_lookups=yes
If you want to send all the email the MTA accepts to DBMail, use the following setting in /etc/postfix/main.cf:
virtual_transport = dbmail-lmtp:<host>:<port>
If you prefer DBMail to be used per domain then add the following in /etc/postfix/transport:
<domain> dbmail-lmtp:<host>:<port>
Where <domain> should replaced by the mail domain you receive mail for. It is possible to have several domain entries here. For <host> and <port> fill out the host and port on which the dbmail-lmtp daemon runs. If unsure about which port they run on, check your dbmail.conf file. The standard port for the lmtp service is port 24. An example of a transport file is below:
example.com dbmail-lmtp:localhost:24 anotherexample.com dbmail-lmtp:localhost:24
Postfix needs to lookup if the recipient domains exist. Otherwise, Postfix will reject your DBMail recipients with a “User unknown in local recipient table” error.
To do this, you need to enable the MySQL- or PGSQL-module in Postfix and add
virtual_mailbox_domains = mysql:/etc/postfix/sql-virtual_mailbox_domains.cf
or for PostgreSQL
virtual_mailbox_domains = pgsql:/etc/postfix/sql-virtual_mailbox_domains.cf
in /etc/postfix/main.cf
After that create the file and add the following MySQL-statements (adjust it to your needs if you use Postgres):
user = <SQL-username> password = <SQL-password> hosts = <SQL-host> dbname = <SQL-database> query = SELECT DISTINCT 1 FROM dbmail_aliases WHERE SUBSTRING_INDEX(alias, '@', -1) = '%s';
For postgresql replace the query by
query = SELECT DISTINCT 1 FROM dbmail_aliases WHERE SUBSTRING(alias FROM POSITION('@' in alias)+1) = '%s';
The query MUST return a non-domain value (just use “1”) if the queried domain exists or a empty set if it doesn't exist. Returning domains here will break the delivery chain of Posfix!
Note: If you use mail addresses as usernames in DBMail, you also have to include 'dbmail_user' in the SQL-query.
If you want Postfix to check the recipient addresses to reduce load on DBMail by false email addresses, add
virtual_mailbox_maps = mysql:/etc/postfix/sql-virtual_mailbox_maps.cf
or for PostgreSQL
virtual_mailbox_maps = pgsql:/etc/postfix/sql-virtual_mailbox_maps.cf
in /etc/postfix/main.cf and add the following content (MySQL):
user = <SQL-username> password = <SQL-password> hosts = <SQL-host> dbname = <SQL-database> query = SELECT 1 FROM dbmail_aliases WHERE alias='%s';
For postgresql replace the query by
query = SELECT DISTINCT 1 FROM dbmail_aliases WHERE alias= '%s';
Make sure not to return the addresses !!!
If you want to use wildcards (user@ and @domain) with postgresql, use this query:
query = SELECT DISTINCT 1 FROM dbmail_aliases where alias='%s' OR alias=SUBSTRING('%s' FROM POSITION('@' in '%s')) OR ( ( SELECT DISTINCT 1 FROM dbmail_aliases WHERE SUBSTRING(alias FROM POSITION('@' in alias)+1) = SUBSTRING('%s' FROM POSITION('@' in '%s')+1) )=1 AND alias=SUBSTRING('%s' FOR POSITION('@' in '%s')));
It searches for the exact match (my@cow.com), then a matching domain wildcard (@cow.com). The subselect in the middle prevents the system from accepting mail for valid users at invalid domains (my@moose.com). The last match (AND) allows user wildcards for accepted domains.
The interaction here seems strange, but it should match the dbmail rules:
- exact match
- user wildcard with valid domain (domain mentioned somewhere in the alias table)
- domain wildcard
Using Piped SMTP Delivery
in /etc/postfix/master.cf add:
dbmail-deliver unix - n n - - pipe
flags= user=<dbmailuser>:<dbmailgroup>
argv=/usr/local/sbin/dbmail-deliver -d ${recipient} -r ${sender}
where <dbmailuser> and <dbmailgroup> should be the user and group the dbmail-smtp program should run as. The ${recipient} and ${sender} fields are filled in by Postfix.
To send all email to DBMail, add this in /etc/postfix/main.cf
virtual_transport = dbmail-smtp:
If you want to decide whether or not to send to DBMail per domain, add this in /etc/postfix/transport:
<domain> dbmail-smtp:
See the section on running Postfix with LMTP if you don't understand the transport file.
now run:
# postmap /etc/postfix/transport # postfix reload
And your mail will be delivered!
Additional Notes
It's possible to use dbmail-lmtp on some domains, and dbmail-deliver on others. Just make both entries in /etc/postfix/master.cf and add transport entries for both.