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Usage

Usage​

  • Reply and the add-on adds originals automatically — or asks first, if enabled in Options.
  • De‑duplicated by filename; S/MIME parts are always skipped. Inline images are restored in the reply body by default (disable via "Include inline pictures" in Options).
  • Blacklisted attachments are also skipped (case‑insensitive glob patterns matching filenames, not paths). See Configuration.

What happens on reply​

  • Detect reply → list original attachments → filter S/MIME + inline → optional confirm → add eligible files (skip duplicates) → restore inline images in body.

Strict vs. relaxed pass: The add‑on first excludes S/MIME and inline parts from file attachments. If nothing qualifies, it runs a relaxed pass that still excludes S/MIME/inline but tolerates more cases (see Code Details). Inline images are never added as file attachments; instead, when "Include inline pictures" is enabled (the default), they are embedded directly in the reply body as base64 data URIs.

Part typeStrict passRelaxed pass
S/MIME signature file smime.p7sExcludedExcluded
S/MIME MIME types (application/pkcs7-*)ExcludedExcluded
Inline image referenced by Content‑ID (image/*)Excluded (restored in body*)Excluded (restored in body*)
Attached email (message/rfc822) with a filenameNot addedMay be added
Regular file attachment with a filenameMay be addedMay be added

* When "Include inline pictures" is enabled (default: ON), inline images are embedded in the reply body as base64 data URIs rather than added as file attachments. See Configuration.

Example: Some attachments might lack certain headers but are still regular files (not inline/S/MIME). If the strict pass finds none, the relaxed pass may accept those and attach them.

Cross‑reference​

  • Forward is not modified by design (see Limitations below).
  • For reasons an attachment might not be added, see “Why attachments might not be added”.

Behavior Details​

  • Duplicate prevention: The add-on marks the compose tab as processed using a per‑tab session value and an in‑memory guard. It won’t add originals twice.
  • Closing and reopening a compose window is treated as a new tab (i.e., a new attempt is allowed).
  • Respect existing attachments: If the compose already contains some attachments, originals are still added exactly once, skipping filenames that already exist.
  • Exclusions: S/MIME artifacts and inline images are excluded from file attachments. If nothing qualifies on the first pass, a relaxed fallback re-checks non‑S/MIME parts. Inline images are handled separately: they are restored in the reply body as data URIs (when enabled).
    • Filenames: smime.p7s
    • MIME types: application/pkcs7-signature, application/x-pkcs7-signature, application/pkcs7-mime
    • Inline images: any image/* part referenced by Content‑ID — excluded from file attachments but embedded in the reply body when "Include inline pictures" is ON
    • Attached emails (message/rfc822): treated as regular attachments if they have a filename; they may be added (subject to duplicate checks and blacklist).
  • Blacklist warning (if enabled): When candidates are excluded by your blacklist, the add-on shows a small modal listing the affected files and the matching pattern(s). This warning also appears in cases where no attachments will be added because everything was excluded.

Keyboard shortcuts​

  • Confirmation dialog: Y/J = Yes, N/Esc = No; Tab/Shift+Tab and Arrow keys cycle focus.
    • The “Default answer” in Configuration sets the initially focused button.
    • Enter triggers the focused button. Tab/Shift+Tab and arrows move focus for accessibility.

Keyboard Cheat Sheet​

KeysAction
Y / JConfirm Yes
N / EscConfirm No
EnterActivate focused button
Tab / Shift+TabMove focus forward/back
Arrow keysMove focus between buttons
Default answerSets initial focus (Yes or No)

Limitations​

  • Forward is not modified by this add-on (Reply and Reply all are supported).
  • Very large attachments may be subject to Thunderbird or provider limits.
    • The add‑on does not chunk or compress files; it relies on Thunderbird’s normal attachment handling.
  • Encrypted messages: S/MIME parts are intentionally excluded.

Why attachments might not be added​

  • Inline images are not added as file attachments. When "Include inline pictures" is ON (the default), they are embedded in the reply body as data URIs instead. If the setting is OFF, inline images are removed entirely. See Configuration.
  • S/MIME signature parts are excluded by design: filenames like smime.p7s and MIME types such as application/pkcs7-signature or application/pkcs7-mime are skipped.
  • Blacklist patterns can filter candidates: see Configuration; matching is case‑insensitive and filename‑only.
  • Duplicate filenames are not re‑added: if the compose already contains a file with the same normalized name, it is skipped.
  • Non‑file parts or missing filenames: only file‑like parts with usable filenames are considered for adding.

See also

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