Hi Andrew
You might want to try a factory reset first of all if you are having problems with your NAS. Then manually configure the device (do not restore a configuration backup). This sometimes helps with strange issues. You shouldn't loose your data in doing so - but as always a backup is a good idea.
If your drive(s) still do not spin down, double check the power management settings in the NAS's web interface. I'm assuming that you are not running any third party modifications on the NAS or that downloads/torrents are scheduled? This would keep the drive awake.
Not sure about the temperature now, seems high for an "ECO" drive.
Regarding speed, how are you connected to your NAS and what speeds are you seeing? It's been written a few times that these boxes aren't very fast. There are a few speed tests posted on this forum.
Not sure about the email. Assuming that the domain, ports and credentials are set correctly, I can only guess that your mail server requires something that your NAS isn't providing, such as secure authentication.