IRC is used by Electrum server to find 'peers' - other Electrum servers. The current list can be seen by running:
electrum-server peers
The following config file options are used by the IRC part of Electrum server:
[server]
irc = yes
irc_nick = server nickname
host = fqdn.host.name.tld
#report_host = fqdn.host.name.tld
#report_stratum_tcp_port = 50001
irc is used to determine whether the IRC thread will be started or the
Electrum server will run in private mode (default). In private mode,
electrum-server peers will always return an empty list.
host is a fully-qualified domain name (FQDN) of your Electrum server. It is
used both when binding the listener for incoming client connections and as part
of the realname field in IRC (see below).
report_host is a an optional fully-qualified domain name (FQDN) of your Electrum server
instead of host. It is used as part of the name field in IRC for incoming client connections.
This is useful in a NAT setup where you bind to a private IP locally but have an external IP
set up at your router and external DNS.
report_stratum_tcp_port, report_stratum_tcp_ssl_port are optional settings for a port number to be reported in the
IRC name field without actually binding this port locally. This is useful in a NAT setup
where you might want to bind to a high port locally but DNAT a different possibly privileged
port for inbound connections
irc_nick is a nick name that will be appended to the E_ suffix when
composing the IRC nickname to identify your server on #electrum.
Please note the IRC name field can only contain 50 chars and will be composed
of host + protocol version number + Port numbers for the various protocols.
Please check whether port numbers are cut off at the end
Example of port forwarding using iptables: iptables -t nat -A PREROUTING -p tcp --dport 110 -j REDIRECT --to-ports 50002