Textbook-l is not yet listed on gmane.org http://mail.wikipedia.org/mailman/listinfo/textbook-l
If no objections I will ask gmane to add Textbook-l
Now all wikipedia lists are using the gmane.science.linguistics.wikipedia* hierarchy.
Whit the new "wikimedia" name i propose to use the gmane.org.wikimedia.* hierarchy for all wikimedia lists.
So for Textbook-l gmane.org.wikimedia.textbook
The other lists can become like this; gmane.org.wikimedia.wikipedia.technical
(but this move will have to wait until the winter afther a software change at gmane.org)