You can't undelete. What you have to do is send those emails from the Trash folder to yourself. Only way I've figured out how to do this.
-- You received this message because you are subscribed to the Google Groups "K-9 Mail" group. To unsubscribe from this group and stop receiving emails from it, send an email to k-9-mail+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.