File-based Storage with Metadata

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Retrieval and Sync When a user opens their mailbox, the server queries the database using SQL or API calls to fetch: List of emails Preview data Full messages (on request) Threading and conversation history Popular Database Types Used by Email Servers 1. Relational Databases (SQL) Examples: MySQL, PostgreSQL, Microsoft SQL Server Structure: Tables with rows and columns Use Case: Ideal for smaller to medium-scale deployments with strict schema enforcement 2. NoSQL Databases Examples: MongoDB, Couchbase, Cassandra Structure: Document-based or key-value Use Case: Great for large-scale email providers like Gmail due to flexibility and scalability 3.

Indexing Some email servers like Dovecot store actual emails in telegram database flat files (Maildir or mbox) and maintain indexes in lightweight databases like SQLite for faster search. 4. Custom Hybrid Systems Enterprise solutions like Microsoft Exchange or Zimbra often use a combination of proprietary database systems and file storage optimized for email operations. Examples of Email Server Software and Their Storage Techniques Let’s look at how some well-known email servers handle multi-user email storage: 1.


Microsoft Exchange Server Uses a proprietary storage engine called Extensible Storage Engine (ESE). Emails are stored in EDB (Exchange Database) files. Supports multi-tenant environments with granular access control and search indexing. 2. Gmail (Google Workspace) Uses Google Spanner, a globally distributed relational database. Highly optimized for real-time search, duplication handling, and encryption. Designed for scalability, handling billions of emails daily. 3. Zimbra Stores emails in MySQL databases and file systems. Metadata and relationships are stored in structured tables.