When a remote BBS/Mailer attempts a inbound connection it uses a specified
domain name provided in the nodelist or specified in the remote mailer's
config. Then via DNS that DN is associated to an IP that is assigned to your
nic or in some cases your router. Essentially BBBS listens on the specified IP
for an incoming connection.
For outbound connections BBBS uses the most recent compiled nodelist OR any
[node_remap] settings specified in BBBS's external.bbb file to know to what
domain name or IP to make an outbound connection to.