Overview

Lookup lists function similarly to in-memory stores like Redis but with a key distinction: lookup lists are static and do not support write operations. Lookup lists are ideal for use cases where values remain unchanged during server operation.

The primary way to interact with lookup lists is through expressions using specialized functions such as key_get, counter_get, and others. These functions allow administrators to query values from the lists and dynamically evaluate configuration settings based on predefined key-value pairs. Lookup lists introduce flexibility into the configuration process, making it easy to adapt the server's behavior to specific operational needs.

Stalwart Mail Server supports both local and remote lookup lists:

• Local lookup lists are defined directly within the server's configuration file, making them suitable for scenarios where all necessary key-value pairs are known in advance. These lists are static and remain entirely under the server's control, ensuring straightforward and predictable management.
• Remote lookup lists, on the other hand, are retrieved over HTTP, allowing the server to access key-value pairs stored externally. This approach is particularly useful in dynamic environments where configurations need to be managed centrally or updated independently of the server's local settings. By enabling access to remote data sources, the server facilitates seamless integration with external configuration systems.