Wheezy: exim4 + mailman it is not sending messages.

[latinfo@vcn.bc.ca]

Hello
i hope you can point me to a trusted doc to read, or tell me what to do.
I read a very rude message coming from the exim4's manteiner; mailman does
not have a man page, and the debian.README is not clear enough to catch
the procedure to make mailman to work.

I did the installation:
# apt-get install mailman OK

It said create mailman list OK
It said that i have to copy ##List aliases to /etc/aliases OK i did it
it said run # newaliases OK i did it

exim sent the creation list messages, but when a user is subscribed, the
user receives the confirmation message, then, replaying does not work. The
web subscription works correctly.

exim4 mainlog says:
R=system_aliases defer (-30): pipe_transport unset in system_aliases router

README.debian mentions 2 different methods, but it is absolutely confuse.

Could somebody help please?

thanks so much.