If you want to have your own server to manage your mail, you should understand that you need to configure this server to work correctly.
First, choose a plan. Since you have a fairly large flow of messages, you need a powerful VPS to handle such mailings.
I think that the following
VPS configurations will be enough for you to start with - 4 GB of RAM, 2 CPUs, 100 GB NVMe SSD. You can get this plan for $12 from hostpro.com. If necessary, you can upgrade to more resources.
Next, you need to configure the server, for this you can install the CWP or cPanel control panel. Usually, when installing the control panel, everything you need for the correct operation of the server and its mail is installed.
After that, you need to configure DNS zones - DKIM, SPF, DMARC, MX, PTR - so that spambots do not add IPs to their blacklists.
The server hostname should be directed to the server IP address (for example, server.exmp.com in record A should have the IP address of your VPS).
When everything is set up and the DNS zone is updated, you need to test the work and fix errors as they occur.
Usually this is just the tip of the iceberg)
I would recommend that you contact technical support to help you set up a server for mail. The guys at hostpro.com can help with this no problem, you just need to contact them and provide a technical specification.