mbox splitter

mbox splitter is a file-based data processing tool that partitions large mailbox archives into smaller chunks. It enables IT administrators, data engineers, and compliance teams to segment mail stores for migration or archival without altering message content. The tool targets environments where mailbox size, transfer windows, or retention policies require per-file limits, controlled subsets, or parallel processing. It supports standard MBOX formats and common variants, preserving headers and MIME parts so messages remain intact. By producing consistently named outputs, it eases automated ingest, backup scripting, and audits.
Conceptually, the tool streams through the input, detecting message boundaries via the familiar From header and appending messages to the current chunk until a threshold is reached. It can operate in three modes: by_messages, by_size, or by_date, each delivering deterministic chunk boundaries and preserving the original order. Optional options include gzip compression, per-chunk indices or manifests, and simple filters. Outputs are plain MBOX files suitable for import into mail servers or archival systems.
Who benefits? System administrators migrating archives, developers validating data pipelines, and compliance teams needing auditable backups. Unique differentiators include streaming processing to handle multi-GB files, border-preserving parsing across mboxo/mboxrd variants, and straightforward file naming with minimal configuration. Use cases span server migrations, scheduled backups, data sharing for analysis, and test datasets for tooling.