How to activate the sending of e-mail notifications of new PRs to the responsibles?

[Raquel Toribio]

Is gnats supposed to send e-mail messages to the responsible of a PR as well
as the people who should be notified.
I set in the categories file:

doc:Documentation Issues:RT:RT,AN

And RT, And AN are defined in the responsible file as:
AN:Alejandro Nieto:Alejandro.Nieto@mdsnetworks-es.com
RT:Raquel Toribio:Raquel.Toribio@mdsnetworks-es.com

Nevertheless, when I submit a PR of the doc category, only the administrator
of gnats is getting an e-mail. And, looking at the maillog traces, I do not
see that gnats tries to send messages to either RT nor AN at all. Does
anybody know if I have to set something else to activate the sending of
notifications to the responsibles of PRs?