The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted as “all IPv4 interfaces” and “all IPv6 interfaces”, respectively. In each case, Exim tells the TCP/IP stack to “listen on all IPvx interfaces” instead of setting up separate listening sockets for each interface. The default value of local_interfaces is
local_interfaces = 0.0.0.0
when Exim is built without IPv6 support; otherwise it is:
local_interfaces = <; ::0 ; 0.0.0.0
Thus, by default, Exim listens on all available interfaces, on the SMTP port.
30.2 Use of the $host and $host_address variables
At the start of a run of the smtp transport, the values of $host and $host_address are the name and IP address of the first host on the host list passed by the router. However, when the transport is about to connect to a specific host, and while it is connected to that host, $host and $host_address are set to the values for that host. These are the values that are in force when the helo_data, hosts_try_auth, interface, serialize_hosts, and the various TLS options are expanded.
Just some quotes from the documentation that may help to understand the cnofig file.
try just one ip in the local_interfaces = xxx.xxx.xxx.xxx