Ah I need to buy my own block of ip addresses? Is that what I need to do? And then connect those ip addresses to my computer that I run at home / office?
Sorry if the question is a bit noob, feel free to point me at any resources and I can do some reading myself too
Most likely you don't buy IP addresses outright. You sign a business Internet contract with your ISP that has a fixed IP address. You essentially lease that IP address from your ISP. You will stipulate in the contract that the IP address will be used to send/receive emails, because otherwise ISPs may block SMTP traffic completely.
Once you get big enough, you can consider buying an IP address prefix, getting your Autonomous System number, setting up peering, etc. For example Mailchimp seems to have AS14782.
Sorry if the question is a bit noob, feel free to point me at any resources and I can do some reading myself too