[Evolution] how delete local copies (IMAP)

[Martin Reuter <mreuter gmx de>]

Hi,

I use IMAP with evolution and need to free local disk space ( .evolution is getting too large).

So I'd like to keep the server copies, just delete local copies of older emails. It's OK to keep the header 
locally, but not the full body or even attachments. How can that be done?
I use version 2.12.3 and don't think I can update easily (network setup at work).

Thanks