Auto-resolve Apple Mail V10 accounts via Accounts4.sqlite

[schlabrendorff]

Builds upon PR #166

Motivation

The previous import-emlx command required users to manually specify both an email identifier and a mail directory:

msgvault import-emlx me@gmail.com ~/Library/Mail/V10/AAAAAAAA-BBBB-CCCC-DDDD-EEEEEEEEEEEE

Especially for importing V10 folder (#157) this is suboptimal.

This was painful for several reasons:

1. Opaque GUIDs: Apple Mail V10 stores each account under a UUID directory (e.g. AAAAAAAA-BBBB-CCCC-DDDD-EEEEEEEEEEEE). There's no obvious way to know which GUID belongs to which email account without digging into Apple's internal databases.
2. One account at a time: Users with multiple accounts (Gmail, Yahoo, iCloud, Exchange) had to run the command once per account, manually mapping each GUID.
3. Error-prone: Getting the GUID-to-email mapping wrong means messages get filed under the wrong source, which is hard to fix after the fact.

Apple already maintains this mapping in ~/Library/Accounts/Accounts4.sqlite. By reading it, we can auto-discover all accounts and import them in one shot.

Summary

• Add internal/applemail package that reads ~/Library/Accounts/Accounts4.sqlite to map V10 directory GUIDs to email addresses, resolving child→parent account relationships (IMAP, Exchange, "On My Mac")
• Rework import-emlx command from import-emlx <email> <mail-dir> to import-emlx [mail-dir] with auto-discovery — users no longer need to manually figure out which GUID maps to which email
• Add --accounts-db, --account (repeatable filter), and --identifier (manual fallback) flags
• Export emlx.IsUUID() for reuse across packages

New UX

Before — one account at a time, manual GUID mapping:

msgvault import-emlx me@gmail.com ~/Library/Mail/V10/AAAAAAAA-BBBB-CCCC-DDDD-EEEEEEEEEEEE
msgvault import-emlx me@yahoo.com ~/Library/Mail/V10/11111111-2222-3333-4444-555555555555
msgvault import-emlx me@icloud.com ~/Library/Mail/V10/FFFFFFFF-0000-1111-2222-333333333333
# ... repeat for each account, hoping you got the GUIDs right

After — all accounts in one command:

# Import everything (defaults to ~/Library/Mail)
msgvault import-emlx

# Or with explicit path
msgvault import-emlx ~/Library/Mail

# Filter to just one account
msgvault import-emlx --account me@gmail.com

# Manual fallback still works for non-V10 layouts
msgvault import-emlx ~/Downloads/old-mail/INBOX.mbox --identifier me@gmail.com

Example output from auto-discovery:

Discovered 4 account(s):
  - alice@gmail.com (Google)
  - On My Mac
  - alice@yahoo.com (Yahoo!)
  - alice@icloud.com (iCloud)

Importing alice@gmail.com (Google)...
Import complete.
  Mailboxes:      3 discovered, 3 imported
  Processed:      809 messages
  Added:          809 messages
  ...

Importing alice@yahoo.com (Yahoo!)...
Import complete.
  Mailboxes:      13 discovered, 13 imported
  Processed:      10908 messages
  Added:          10907 messages
  ...

=== Grand Total ===
  Mailboxes:      52 discovered, 52 imported
  Processed:      39038 messages
  Added:          34590 messages
  Updated:        0 messages
  Skipped (dup):  4448 messages
  Errors:         0

How it works

1. Scans mail-dir for V*/ directories containing UUID subdirectories
2. Opens Accounts4.sqlite read-only and resolves each GUID using COALESCE(child.ZUSERNAME, parent.ZUSERNAME) to handle IMAP child accounts that inherit email from their parent
3. Imports each account sequentially, printing per-account summaries and a grand total
4. Accounts without an email (e.g. "On My Mac") use their description as the identifier
5. GUIDs not found in the accounts DB are skipped with a warning

[roborev-ci]

roborev: Combined Review (baf2124)

**
Verdict:** The PR successfully implements Apple Mail V10 account auto-discovery, but introduces medium-severity issues regarding directory selection logic and CLI backward compatibility.

Medium

Stale Data Import Risk
File: [accounts.go:181](/home/roborev/repos/msg
vault/internal/applemail/accounts.go:181)
V10AccountDir returns the first V* match for a GUID. If the same GUID exists in multiple version directories (e.g., V2, V10, V11), the
import source selection is lexicographic rather than selecting the latest/active version, which may result in importing stale data.
Suggested fix: Parse the numeric version from the V<digits> directory names and select the highest version containing the GUID, or explicitly constrain the selection to the intended version.

CLI Backward Compatibility Regression

File: import_emlx.go:54
The CLI argument contract changed from requiring <identifier> <mail-dir> to accepting [mail -dir] with an --identifier flag, now enforcing MaximumNArgs(1). Existing scripts utilizing the old two-argument format will hard-fail, causing a functional regression for upgrading users.
Suggested fix: Support both forms for a transition period (e.g., using RangeArgs( 0,2)), map legacy arguments to identifier and mailDir, and emit a deprecation warning.

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Synthesized from 3 reviews (agents: codex, gemini | types: default, security)