Setting up your database

Mailman uses the SQLAlchemy ORM to provide persistence of data in a relational database. By default, Mailman uses Python’s built-in SQLite3 database, however, SQLAlchemy is compatible with PostgreSQL and MySQL, among possibly others.

Currently, Mailman is known to work with either the default SQLite3 database, or PostgreSQL. (Volunteers to port it to other databases are welcome!). If you want to use SQLite3, you generally don’t need to change anything, but if you want Mailman to use PostgreSQL, you’ll need to set that up first, and then change a configuration variable in your /etc/mailman.cfg file.

Two configuration variables control which database Mailman uses. The first names the class implementing the database interface. The second names the URL for connecting to the database. Both variables live in the [database] section of the configuration file.


As mentioned, if you want to use SQLite3 in the default configuration, you generally don’t need to change anything. However, if you want to change where the SQLite3 database is stored, you can change the url variable in the [database] section. By default, the database is stored in the data directory in the mailman.db file. Here’s how you’d force Mailman to store its database in /var/lib/mailman/sqlite.db file:

url: sqlite:////var/lib/mailman/sqlite.db


First, you need to configure PostgreSQL itself. This Ubuntu article may help. Let’s say you create the mailman database in PostgreSQL via:

$ sudo -u postgres createdb -O $USER mailman

You would then need to set both the class and url variables in mailman.cfg like so:

class: mailman.database.postgresql.PostgreSQLDatabase
url: postgres://myuser:mypassword@mypghost/mailman

That should be it.

If you have any problems, you may need to delete the database and re-create it:

$ sudo -u postgres dropdb mailman
$ sudo -u postgres createdb -O myuser mailman

My thanks to Stephen A. Goss for his contribution of PostgreSQL support.

Database Migrations

Mailman uses Alembic to manage database migrations. Let’s say you change something in the models, what steps are needed to reflect that change in the database schema? You need to create and enter a virtual environment, install Mailman into that, and then run the alembic command. For example:

$ virtualenv -p python3 /tmp/mm3
$ source /tmp/mm3/bin/activate
$ python develop
$ alembic -c src/mailman/config/alembic.cfg revision --autogenerate -m

This would create a new migration which would automatically be migrated to the database on the next run of Mailman. Note that the database needs to be in the older state so that Alembic can track the changes in the schema and autogenerate a migration. If you don’t have the database in the older state you can remove the –autogenerate flag in the above command. It would then create a new empty revision which you can edit manually to reflect your changes in the database schema.

People upgrading Mailman from previous versions need not do anything manually, as soon as a new migration is added in the sources, it will be automatically reflected in the schema on first-run post-update.

Note: When auto-generating migrations using Alembic, be sure to check the created migration before adding it to the version control. You will have to manually change some of the special data types defined in mailman.database.types. For example, mailman.database.types.Enum() needs to be changed to sa.Integer(), as the Enum type stores just the integer in the database. A more complex migration would be needed for UUID depending upon the database layer to be used.