I've searched high and low on Google for this and can only find header_cache
for setting the cache dir only. I need to find a way to set the max size of the header cache and the max size of the message cache dir. That one I cannot find.
I can turn off header cache using:
folder-hook =spam 'set header_cache=""'
But I don't want to turn it off, I just want to limit it's size :(