Stalwart Mail Server offers two different storage options for email messages and other types of blobs (binary large objects), like Sieve scripts which are used for mail filtering. The server can store this data either locally or on S3-compatible storage, offering flexibility to suit different operational needs.
When using local storage, email messages are stored in the local disk using the Maildir format. This popular storage format stores each email message as a separate file within a specific directory structure, which reduces the need for file locks and optimizes operations such as message delivery and deletion.
For distributed and larger-scale implementations, Stalwart Mail Server supports the use of S3-compatible storage services. S3, or Simple Storage Service, is a scalable object storage protocol used by many cloud providers. By using an S3-compatible service, Stalwart can store emails and blobs on remote servers, facilitating large-scale storage management, easy data replication, and backup, making it a viable option for businesses seeking robustness and scalability.