Copy markdown from Emacs, paste formatted content directly into GMail

elisp.el

(defun formatted-copy ()
  "Export region to HTML, and copy it to the clipboard."
  (interactive)
  (save-window-excursion
    (let* ((buf (org-export-to-buffer 'html "*Formatted Copy*" nil nil t t))
           (html (with-current-buffer buf (buffer-string))))
      (with-current-buffer buf
        (shell-command-on-region
         (point-min)
         (point-max)
         "pandoc -f gfm -t html5 | pbcopy_html"))
      (kill-buffer buf))))

(global-set-key (kbd "C-M-c") 'formatted-copy)

pbcopy_html

#!/usr/bin/env swift

import Cocoa
import Darwin

let pasteboard = NSPasteboard.general

guard let data = try? FileHandle.standardInput.readToEnd() else {
    exit(1)
}

pasteboard.clearContents()
pasteboard.setData(data, forType: .html)