Outlook invites

Please tell me how I get to send and receive meeting invites from people who
are not on the same network. E.g. I get meeting invites from another company
and that request comes through as an email not an invite. I actually then
have to go into my calender and add it as an appointment.

How can I or them send it and receive it as a meeting request and accept and
it pops it into my calender -----without sharing my calender? Happy to
share my calender to show busy but not happy to share details...