Foundry376/Mailspring · error

Invalid mailto URI

Error message

Invalid mailto URI

What it means

Validation guard at the top of performMailtoUnsubscribe: the value taken from the message's List-Unsubscribe header did not start with 'mailto:' (case-insensitive), so it cannot be opened as a pre-filled unsubscribe draft. Indicates a malformed or unexpected header value, not a runtime failure.

Source

Thrown at app/internal_packages/list-unsubscribe/lib/unsubscribe-service.ts:139

    return {
      success: false,
      error: err instanceof Error ? err.message : 'Unknown error occurred',
    };
  }
}

/**
 * Opens the composer with a pre-filled unsubscribe email for mailto: links.
 *
 * This allows the user to review the email before sending, as recommended
 * for transparency.
 *
 * @param mailtoUri - The mailto: URI from the List-Unsubscribe header
 */
export function performMailtoUnsubscribe(mailtoUri: string): void {
  if (!mailtoUri.toLowerCase().startsWith('mailto:')) {
    throw new Error('Invalid mailto URI');
  }

  // Use the application's openUrl handler which routes to DraftStore._onHandleMailtoLink
  // This creates a draft and opens it in the composer for user review
  const sanitizedUri = encodeURI(decodeURI(mailtoUri));
  require('@electron/remote').getGlobal('application').openUrl(sanitizedUri);
}

/**
 * Opens the unsubscribe URL in the user's default browser.
 *
 * This is used as a fallback when one-click is not available.
 *
 * @param url - The HTTP/HTTPS URL to open
 */
export function performWebUnsubscribe(url: string): void {
  if (!/^https?:\/\/.+/i.test(url)) {
    throw new Error('Invalid URL');

View on GitHub (pinned to 648c685d60)

Solutions

1. Validate/normalize the List-Unsubscribe value before choosing the mailto path
2. Fall back to performing a web unsubscribe or showing the raw link when the header is malformed
3. Return a structured {success:false,error} result instead of throwing so callers can degrade gracefully

When it happens

Trigger: Thrown at app/internal_packages/list-unsubscribe/lib/unsubscribe-service.ts:139 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of Foundry376/Mailspring@648c685d60 (2026-09-03). Data as JSON: /api/errors/3b7ae8c4d74c9098. Report an issue: GitHub.