fetcher

The fetcher package handles all email retrieval operations over IMAP. It connects to mail servers, fetches email headers and bodies, manages attachments, and supports mailbox operations like delete, archive, and move.

Architecture

This package is the IMAP client layer for Matcha. It:

• Establishes TLS/STARTTLS connections to IMAP servers based on account configuration
• Fetches email lists with pagination and per-account filtering (using FetchEmail to match relevant messages)
• Retrieves full email bodies with MIME part traversal (preferring HTML over plain text)
• Handles attachments including inline images (with CID references) and file attachments
• Supports S/MIME decryption (opaque and enveloped) and detached signature verification
• Provides mailbox operations: delete (expunge), archive (move), and folder-to-folder moves
• Exposes both mailbox-specific and convenience functions (e.g., FetchEmails defaults to INBOX)
• Supports XOAUTH2 SASL authentication for Gmail OAuth2 accounts (see xoauth2.go)

XOAUTH2

The xoauth2.go file implements the XOAUTH2 SASL mechanism as a sasl.Client. When an account uses auth_method: "oauth2", the fetcher calls config.GetOAuth2Token() to get a fresh access token, then authenticates the IMAP connection using this SASL client instead of a password. The initial response follows Google's XOAUTH2 protocol: user=<email>\x01auth=Bearer <token>\x01\x01.