+(defun gnus-summary-idna-message (&optional arg)
+ "Decode IDNA encoded domain names in the current articles.
+IDNA encoded domain names looks like `xn--bar'. If a string
+remain unencoded after running this function, it is likely an
+invalid IDNA string (`xn--bar' is invalid).
+
+You must have GNU Libidn (`http://www.gnu.org/software/libidn/')
+installed for this command to work."
+ (interactive "P")
+ (if (not (and (condition-case nil (require 'idna)
+ (file-error))
+ (mm-coding-system-p 'utf-8)
+ (executable-find (symbol-value 'idna-program))))
+ (gnus-message
+ 5 "GNU Libidn not installed properly (`idn' or `idna.el' missing)")
+ (gnus-summary-select-article)
+ (let ((mail-header-separator ""))
+ (gnus-eval-in-buffer-window gnus-article-buffer
+ (save-restriction
+ (widen)
+ (let ((start (window-start))
+ buffer-read-only)
+ (while (re-search-forward "\\(xn--[-0-9a-z]+\\)" nil t)
+ (replace-match (idna-to-unicode (match-string 1))))
+ (set-window-start (get-buffer-window (current-buffer)) start)))))))
+