Steps to reproduce:

1. Add template MSSQL by ODBC to server

Result:

Server turns red since ${MSSQL.HOST} isn't overridden, but set to localhost

Earlier, MSSQL by ODBC used {HOSTS.CONN} to check MSSQL hosts, which makes perfect sense, but from 7.0 and forth, it uses a custom macro, {$MSSQL.HOST}, set to 'localhost' by default. Zabbix still knows perfectly the IP address(es) of the host, but refuses to use what it knows, but rather wants a separate macro for this. This only adds more work. As far as I can see, the only thing actually using this, is net.tcp.service[tcp,\{$MSSQL.HOST},\{$MSSQL.PORT}]), and since that's a simple check, it's run on the server and I daresay most zabbix servers don't run MSSQL.

        - macro: '{$MSSQL.HOST}'
          value: localhost
          description: 'The hostname or IP address of the MSSQL instance.'