Since I'm using a netbook with only 16GB SSD, I want to use most lightweight client possible (hence not Thunderbird)
However, I wasn't able to find an option to download only recent mails, say, more recent than a week, in claws mail.
Is there a way to turn this on? If claws mail does not have it, does any lightweight mail client have it? On a related note, how may I see the space that all my mails are occupying?
Geary is a lightweight mail client for GNOME 3. It only downloads recent email by default. This can be configured in the Accounts dialog.
In any case, Postler was definitely taking this approach, but it was discontinued (and officially suggesting Geary instead).
Claws Mail won't download all msg bodies automatically (depending on the settings you choose), so this shouldn't be a problem. If the msg cache is getting too big, use 'discard folder cache' from the Folder Properties.
