I have a Debian server with Spam Assassin 3.1.7 and Postfix v. 2.3.8 .. I started getting Postfix SMTP server error - Insufficient system storage this past couple days. I have 70M of availble space. Mail is flowing but if I get this error, I have delete e-mails with huge attachments for mail to flow again. Since I'm a newbie at this, what files can I safely delete? Any temp files? Cached? Any advise is appreciated.