Working with the local Postfix MTA

Background

The Yoda External User Service (EUS) and the main ruleset send email messages to users. In the standard configuration, the EUS and ruleset send messages directly to a relay server, which would typically be your organization’s email server.

Alternatively, the EUS and ruleset can be configured to send messages to a local Postfix Mail Transfer Agent. Postfix then takes care of delivering the messages to a relay host, such as your organization’s email server.

Advantages

The main advantages of using Postfix rather than sending email messages directly to the organizational email server are:

• If Yoda delivers emails directly to the organizational email server, any connection or availability issues can result in user actions failing. For example, if a Yoda user creates a new external account by adding an email address of a new user to a research group, the user will see an error message if the email server is not available. If Yoda uses Postfix, account creation will succeed, and Postfix will take care of delivering the message asynchronously.
• Postfix automatically retries delivering emails in case of transient errors, whereas Yoda and the EUS don’t have this capability in the default configuration.
• Postfix has proper logging of email message delivery, whereas Yoda and the EUS have very limited email logging in the default configuration. Complete logging makes it possible to verify that emails have been sent, and to find the cause of any problems in case something has gone wrong.
• Postfix can be configured to rewrite internal email addresses to public email addresses, making it possible to deliver email for Yoda accounts with nonexistent email addresses.

In summary, using Postfix as a local MTA makes email delivery more resilient and helps with troubleshooting.

Configuration

Configuration consists of up to four parts:

• Configure Postfix
• Configure Yoda (ruleset) and EUS to send emails to the Postfix instance
• Optionally configure canonical map entries for rewriting email addresses

Postfix

In order to configure Postfix, you will need an account that can be used for sending email messages using Secure SMTP. Example configuration:

enable_postfix: true

postfix_relayhost: smtp.myuniversity.nl
postfix_myhostname: yoda.myuniversity.nl
postfix_relayhost_username: smtpaccount@myuniversity.nl
postfix_relayhost_password: myPassword

Yoda ruleset

Configure the Yoda ruleset and External User Service (EUS) to send email messages via the local Postfix instance:

smtp_server: smtp://localhost:25
smtp_auth: false
smtp_starttls: false

Canonical map

If the Yoda instance has accounts with names that do not relate to real email addresses, the postfix_canonical_map dictionary can be used to make Postfix rewrite addresses. For example:

postfix_canonical_map:
  datamanager@yoda.test: a.admin@uu.nl
  researcher@yoda.test: a.admin@uu.nl

See also

• Troubleshooting email