Keep emails on iCloud but limit the amount on Macbook

Could anyone help me figure out how to keep all my emails (mac.com account) on my iCloud but limit the amount saved to my MacBook? The emails are taking up about 50GB of space but I don't want to delete any of them forever to free up space. I don't need emails on my hard drive beyond a year into the past. Is this possible? Any help would be greatly appreciated. Thanks.