Memory in OSes like OS X should be used since it's faster than the HDD. So the memory should always be at or near 100% in use to get the most performance.
This can alarm old DOS or new users.
But if it's disk space and the email duplicating that sounds like a Trojan or such. Did you happen to install something prior to this issue?
Also, why not empty the recovered messages?
Mac OSX version 10.6.8
Memory 4GB 1067 MHz DDR3
No matter how many applications, documents, etc. I junk my computer's memory immediately fills up again.
This appears to have started when I emailed some photos. Now that email has duplicated itself hundreds of times. When I look at On My Mac - Recovered messages, I find hundreds of copies of this email. Is this a bug, a virus? What should I do? I am trying to throw away that email but I think it is reproducing...