To do this you need to have your server 'known' to the internet so that the rest of the world (including google mail) knows where to push your emails. And then run an MTA on your server (like postfix) that the outside world can connect to, to deliver the email. The MTA is then responsible for delivering to the the spool directory.
I am pretty sure that requires a fixed IP address where your server can be reached, and a server that is online most of the time.
If this is only for a single account, it is much easier to create a special email account somewhere (e.g. gmail) and pick up that email with a cron job that call
fetchmail and delivers to the local MTA. This does not require a fixed IP for the server, nor that the port for the MTA (25) on the server is reachable from the outside world.