Duplicate Email Remover
=======================
Finds and removes duplicate emails across your Thunderbird folders. It
uses the Message-ID header for reliable matching, so a duplicate has to
genuinely be a duplicate — no false positives from similar subjects,
dates, or senders. For the rare message with no Message-ID, it falls
back to subject + sender + size + timestamp-to-the-minute.

Quick start
-----------
1. Click the toolbar icon (envelope-pair) to open the popup.
2. Expand "Folders to scan" and check the folders you want scanned.
Your selections persist across sessions.
3. Choose which copy to keep by default (oldest or newest) and one of
three actions: move duplicates to Trash, delete permanently, or move
to a folder of your choice.
4. Click Scan for Duplicates. The scan opens in a detached window that
stays open even if you click elsewhere in Thunderbird.
5. Each duplicate group shows every copy found. Copies default to KEEP
(green) or DELETE (red) based on your oldest/newest choice. Tap any
row to flip its state; tap the eye icon on a row to preview the
message. Each group must have at least one KEEP.
6. Uncheck any whole group you don't want touched, tick the
confirmation box and click the action button.

Extension-wide preferences live on the Options page: Add-ons and Themes
→ Duplicate Email Remover → Options.

Entry points
------------
- Toolbar button (envelope-pair icon) in Thunderbird's main mail
window — opens the popup with all scan controls and results. This is
the only entry point during normal use.
- Options page — Add-ons and Themes → Duplicate Email Remover →
Options. Sets defaults for future scans (which copy to keep, which
action to take, which folder types to skip, silent mode, diagnostics
on/off).

Options page
------------
- Skip Drafts, Sent, Templates, Outbox, Archives, and Trash — each an
independent checkbox, all default to on. These folders normally hold
intentional copies (drafts vs. sent versions, archived-and-deleted
copies, trashed originals) that shouldn't be treated as duplicates.
- Skip messages already marked deleted on IMAP servers (default on).
- Default keep-strategy (oldest or newest) and default delete action.
- Silent mode to skip the confirmation checkbox (default off,
recommended off).
- Diagnostics mode to log every scanned message and auto-save the log
to your Downloads location after each scan (default off).

Update log
----------
Version 1.2.3
- Filtering the folder tree now also scopes what a scan touches. Before,
folders that were checked but hidden by the account or text filter
were still being scanned — a hazard when a user narrowed the view
expecting to limit scan scope. Only folders visible under the current
filters are now eligible for scanning.
- Folder selection now only responds to a click on the checkbox itself,
not the whole row. Prevents accidentally toggling selection while
scrolling or reading folder names.
- Internal cleanups (removed a duplicate default flag and some dead
code) with no user-visible change.

Version 1.2.2
- Each copy in a duplicate group is now independently KEEP or DELETE;
tap a row to flip just that row, rather than accepting the extension's
auto-selection. A safety guard prevents marking the last remaining
KEEP as DELETE. Preview moved to a small eye icon so the row body is
a clean toggle target.
- New Skip Trash option, default on. Stops treating a message you kept
in one folder and its already-trashed copy as a duplicate.

Version 1.2.1
- Skip Archives now defaults on. Gmail exposes labels as IMAP folders
and its "All Mail" folder contains every message, so scanning
archives makes every Gmail message appear as a duplicate and
deleting from those folders has non-obvious server-side effects.
Turning Skip Archives off shows an inline warning explaining the
risk before proceeding.
- Folder tree hides any folder type currently being skipped, and the
"N of M selected" counter reflects only scannable folders.

Version 1.2.0
- Scans run in a detached window that stays open even if you click
elsewhere in Thunderbird. Setup still happens in the toolbar popup.
- Cancel button next to the progress bar interrupts a running scan
between folders.
- Account filter above the folder tree limits the visible list to one
account at a time. Select all / Select none respect the current
filter so bulk-toggle only touches visible folders.
- Cascade selection toggle in the folder tree header controls whether
checking a folder also checks its subfolders.

Version 1.1.9 – 1.1.10
- When no duplicates are found, the results include a hint about
Thunderbird's local view going out of sync (especially in the
Unified view). Clicking into the source folder or refreshing the
account often makes phantom duplicates disappear.

Version 1.1.3 – 1.1.8
- Diagnostics toggle in the popup and on the Options page. When on,
every scan writes a log to your Downloads location; the filename
includes the version and timestamp. Logs include per-folder message
counts, folder types, and per-message dedup keys.
- The old single "skip special folders" switch was replaced with
independent per-type checkboxes so users can control Drafts, Sent,
Templates, Outbox, and Archives individually.
- Results include a "Per-folder scan counts" breakdown so you can see
exactly which folders were walked and how many messages each
contributed.

Version 1.1.2
- Added a secondary content-based matching key (subject + sender +
size + timestamp-to-the-minute) alongside Message-ID matching, so
copies whose Message-ID differs due to normalization quirks are still
grouped. Message-ID matching now strips angle brackets and
whitespace before comparison.

Version 1.1.1
- Folder list is a collapsible section, collapsed by default, with a
live "N of M selected" summary on the header. Auto-collapses when a
scan starts.
- Preview swaps into the full popup rather than a cramped panel below
results. Back button returns to the same row you tapped.

Version 1.1.0
- Options page introduced with per-user defaults.
- New action alongside Trash and Permanent: move duplicates to a
folder of your choice.
- Clearer results UI. The kept copy is green with a KEEP badge; each
removed copy is red with a DELETE badge. The action button shows the
exact count and action (e.g. "Move 42 Duplicate(s) to Trash") and
updates live as you toggle groups or change the action.

Version 1.0.0
- Initial release. Folder-tree checklist with cascading selection,
persistent settings, Message-ID-based dedup with subject / sender /
date / size fallback, three-way choice (Trash / Permanent), scan
progress, and confirmation checkbox.

Permissions and why
-------------------

- storage — to remember your folder selections and defaults across
popup sessions and Thunderbird restarts. Stored locally, never sent
anywhere.
- downloads — to auto-save the diagnostics log to your Downloads
location when diagnostics mode is on.
- accountsRead — to enumerate accounts and folders, and to know which
folder each message lives in.
- messagesRead — to list messages, read headers, and load the preview
body.
- messagesDelete — to move duplicates to Trash or delete permanently.
- messagesMove — to move duplicates into a folder you choose.

Update log
----------

Version 1.2.2
- Each copy in a duplicate group is now independently KEEP or DELETE;
tap a row to flip just that row, rather than accepting the extension's
auto-selection. A safety guard prevents marking the last remaining
KEEP as DELETE. Preview moved to a small eye icon so the row body is
a clean toggle target.
- New Skip Trash option, default on. Stops treating a message you kept
in one folder and its already-trashed copy as a duplicate.

Version 1.2.1
- Skip Archives now defaults on. Gmail exposes labels as IMAP folders
and its "All Mail" folder contains every message, so scanning
archives makes every Gmail message appear as a duplicate and
deleting from those folders has non-obvious server-side effects.
Turning Skip Archives off shows an inline warning explaining the
risk before proceeding.
- Folder tree hides any folder type currently being skipped, and the
"N of M selected" counter reflects only scannable folders.

Version 1.2.0
- Scans run in a detached window that stays open even if you click
elsewhere in Thunderbird. Setup still happens in the toolbar popup.
- Cancel button next to the progress bar interrupts a running scan
between folders.
- Account filter above the folder tree limits the visible list to one
account at a time. Select all / Select none respect the current
filter so bulk-toggle only touches visible folders.
- Cascade selection toggle in the folder tree header controls whether
checking a folder also checks its subfolders.

Adds diagnostics with automatic write of log to user's configured download location (Preferences → General → Files & Attachments → "Save files to")