NickServ is usually server-side alias on all networks that also checks that we are sending message to Services and if we aren't, the sending is aborted. Try it with `/quote NickServ help` or even `/allserv quote NickServ help`.
I don't recommend anything anymore there, network operators do that now
(ask at \#freenode and they will suggest SASL as reads at
https://freenode.net/faq.shtml#identify ).
Also mention that SASL is SASL PLAIN and to use SASL EXTERNAL you simply
configure CertFP + explain difference between the two mechanisms.