How to keep mail messages on servers for Apple mail? My "late 2013" Mac Pro has a small internal SSD. Since Yahoo Mail and Google Mail have large storage on their servers, I don't see reasons for me to store mail messages on my local SSD. Can Apple Mail client be configured in a way that it only stores, say, 1 month of mail messages locally? Then it can fetch older mail messages on demand. Can I configure Apple Mail to do that?
You can begin with Setting the Download Attachments to None in you Mac Mail.

That is the biggest part of mails anyway, the rest is just text.

If you are up to the task you can then export all attachments out of your Local storage.

They are located in ~/Library/Containers/com.apple.mail/Data/Library/Mail Downloads/

You can also Export all of the mail box, to for example iCloud.
It just makes a copy of it, so you can now delete mails on your Mac, and get them again later.

To do so right click on the mailbox and use Export.

Did you know that for $1/Month you can upgrade your iCloud to 50GB.



Now if you want to automate that, like keep emails for a month then Export, you will need a Automator process for that.