Zoho is great, especially for OP’s use case where they want to manage multiple mailboxes under the same domain. The Zoho cpanel can do all that.

Also Ive never had my outgoing emails rejected.

pfSense is great!!! I bought a Netgate router which comes with pfSense Plus.

OP, consider buying a Netgate router if you want no hassle, or if you’re up for installing an OS then you can put pfSense on a custom platform like ZimaBoard or Protectli.