Features

Automatically attaches files from the original email when replying.
Configurable behavior: attachments can be
- added automatically, or
- added only after confirmation (a small, accessible dialog). In Options you can enable the confirmation and choose the default answer (Yes/No).
Blacklist of filenames (glob patterns) prevents specific files from being attached automatically. Examples: *intern*, *secret*, *passwor*. Matching is case‑insensitive and checks the filename only; provide one pattern per line in Options.
Blacklist warning (optional, enabled by default): when files are excluded by your blacklist, a small modal lists the file and the matching pattern(s). Dark‑mode friendly and keyboard accessible (Enter/Esc to close).
Works with Reply and Reply all. Forward is not modified by this add-on.
Adds originals even if you already attached something yourself; avoids duplicates by filename.
Per‑tab duplicate guard prevents double‑adding in the same compose tab.
Skips S/MIME certificates by default to avoid unnecessary attachments.
Include inline pictures (default: ON). Embedded images are restored directly in the reply body as base64 data URIs, preserving the original inline layout. Disable in Options to skip inline images entirely.

How It Works

On reply, the add-on lists original attachments.
Filters out S/MIME signatures from file attachments; inline images are restored in the body (unless disabled).
Optionally asks for confirmation (keyboard-friendly).
Adds eligible files to your compose, avoiding duplicates by filename.
See “Why attachments might not be added” in Usage for edge cases.

Privacy note: All processing happens locally in Thunderbird. The add-on makes no background network requests.