Missing emails on MacBook but not iPhone

It appears this issue has been a problem off and on for some time. I just noticed that I am receiving many emails on my iPhone that are not showing up on my Mac. I'm missing lots of important emails because of this and don't know what I need to do. Closing Mail on my Mac doesn't make a difference. My Mac is currently on Mojave 10.14.5. (I think.) Does anyone else have this problem? Anyone know how to fix it?

Thanks!