`mail2couch` is a Go-based command-line tool that archives emails from IMAP servers into a CouchDB database. It performs efficient incremental syncs, allows for flexible filtering of folders and messages, and stores attachments natively within CouchDB. Each mail account is stored in a separate database for clear organization.
**How it does it:**
The application is written in Go and uses a `config.json` file to manage CouchDB and IMAP credentials. It leverages the `go-imap` library for IMAP communication and `kivik` for interacting with CouchDB. It maintains a `sync_metadata` document in each CouchDB database to track the last sync time, enabling it to only fetch new messages on subsequent runs. A `sync` mode is available to keep the archive as a 1-to-1 mirror of the server, but the default `archive` mode preserves all fetched mail. The project also includes a comprehensive test suite using Podman to validate its core features.
**Problems, Missing Features, and Suggested Improvements:**
***Primary Weakness: Security:** The application requires storing IMAP and CouchDB passwords in plain text within the `config.json` file. This is a significant security risk.
***Suggestion:** Prioritize adding support for reading secrets from environment variables (e.g., `M2C_COUCH_PASSWORD`) or integrating with a secrets management tool. For services like Gmail, implementing OAuth2 would be a more secure and modern authentication method than app passwords.
***Incomplete Rust Implementation:** The `rust/` directory contains a non-functional placeholder for a Rust version of the tool. This could be confusing for contributors.
***Suggestion:** The `README.md` should explicitly state that the Rust implementation is aspirational and not functional. Alternatively, if there are no plans to develop it, it could be removed to avoid confusion.
***Missing Core Feature: Web Interface:** The `README.md` heavily promotes a future web interface for viewing the archived emails, which is a key feature for making the archive useful. This feature is not yet implemented.
***Suggestion:** This should be the highest priority for new feature development. The existing CouchDB schema is well-suited for this, and implementing CouchDB design documents with list and show functions would be the next logical step.
***Performance for Large-Scale Use:** The application processes accounts and mailboxes sequentially.
***Suggestion:** For users with many accounts or mailboxes, performance could be significantly improved by introducing concurrency. Using Go's concurrency features (goroutines and channels) to process multiple mailboxes or even multiple accounts in parallel would be a valuable enhancement.
***Inefficient Keyword Filtering:** Message filtering by keywords (subject, sender, etc.) is done client-side *after* downloading the messages.
***Suggestion:** Modify the IMAP fetching logic to use server-side `IMAP SEARCH` with keyword criteria. This would reduce bandwidth and processing time, especially for users who only need to archive a small subset of messages from a large mailbox.
***Usability Enhancement: Dry-Run Mode:** Users have no way to test their configuration (especially folder and message filters) without performing a live sync.
***Suggestion:** Implement a `--dry-run` flag that would log which mailboxes and messages *would* be processed and stored, without actually writing any data to CouchDB.
