Just two simple steps – create logging action and rule.

First step

Define action (set action name, remote server IP address, syslog parameters):

/system logging action
add bsd-syslog=yes name=remote_server_x remote= remote-port=514 \
    src-address= syslog-facility=daemon syslog-severity=auto target=\

Second step

Define rule (use action created in the first step, specify desired topics):

/system logging
add action=remote_server_x disabled=no prefix="" topics=system,!snmp,!ntp