Linux + postfix (SMTP) + dovecot (IMAP and POP3) + SPF + DKIM on the host

Point the MX record for your domain to your IP address

Contact your ISP and ask them to set the PTR record for your IP to your hostname

Mail can be handled by a very low end computer, a raspberry pi can handle email for a small number of users

If you have a specific mail machine you would forward the ports you use to that host on your router.