EML External Editor

VS Code language support for RFC 5322 .eml files — email messages saved to disk. This was written to use VS Code / Codium together with the external-editor-revived extension for Thunderbird/Betterbird.

What it does

Adds syntax highlighting that distinguishes:

• Header names (From:, Subject:, etc.) from header values
• Folded continuation lines in long headers
• Quoted reply lines beginning with >
• The signature block, introduced by a -- marker line

It also provides mail-aware paragraph wrapping for plain text message bodies. There is no MIME body decoding or message sending; the extension only edits the .eml text open in VS Code.

Reflow

Alt-Q (Option-Q on macOS) reflows the paragraph containing the cursor, wrapping at the column given by editor.wordWrapColumn (default 72). Quote prefixes (> , > > , etc.) are preserved on every wrapped line, so the structure of quoted replies survives reflow. Headers and the signature block (after a -- marker) are left untouched.

Cmd-/ toggles > on selected lines — useful for converting plain text into a quoted form when writing a reply by hand.

Auto-wrap

By default, typed body text wraps automatically at editor.wordWrapColumn (default 72). The break is placed at the latest whitespace before the wrap column, and quote prefixes such as > or | are preserved on continuation lines.

Auto-wrap skips headers, attribution lines such as On <date>, <name> wrote:, empty quote lines, and the signature block after a -- marker. Pastes are left alone; only single-character typed inserts trigger wrapping. If a line is already longer than editor.wordWrapColumn, editing it will not force a new wrap.

Disable it in user or workspace settings with:

{
  "eml.autoWrap.enabled": false
}

If you also have Rewrap installed

Both this extension and Rewrap (or Rewrap Revived) bind Alt-Q, and VS Code's keybinding resolver doesn't always pick the more specific when clause — so Rewrap's binding can end up winning on .eml files. Symptom: Alt-Q on an .eml file does nothing visible.

The reliable fix is a user-level keybinding override (user keybindings always win over extension-contributed ones). Open your user keybindings.json via Cmd-K Cmd-S → page icon at the top right, and add:

{
  "key": "alt+q",
  "command": "eml.reflow",
  "when": "editorTextFocus && editorLangId == eml"
}

Scope

This extension handles single-message .eml files only. Mailbox files (.mbox), which concatenate many messages with From-prefixed separator lines, are not supported.

License

Terms are in the LICENSE.txt file bundled with this extension.