Once you have joined an email network you will receive a welcome
message. This includes the address you need to use to send a
message to everybody in the email network.
You should also be able to find the address as part of the
information at the top of each message you receive. If in doubt,
you can contact the network administrator.
When you send a message it automatically goes to everybody who
is a member of the network. As this includes you, you'll receive
your own copy of the message as well which confirms that it has
also gone to everybody.