I have been running a Debian email server for about 200 users for a year or so now. It has run nearly perfectly this whole time. The only things that really run are apache (for webmail), exim, qpopper, and Vexira Mailarmor.

I started having this problem just today. As soon as the machine boots up, 418MB of my 512MB of RAM are used up. This is WITHOUT running exim, vexira, or qpopper. The only thing running at startup time is apache. When I run "top", and sort by mem usage, the top 5 processes are all apache, and they are only running about 3mb (0.6 percent) of the total used memory each. NONE of the swap file (another 512MB, on a seperate partition), is being used.

If I try to run exim, with the antivirus program, the remaining ~60MB of memory gets eaten up and the machine hangs almost immediately, the swap is never touched. I checked disk usage, and none of the partitions are above 10% usage.

It looks as if there is ~400MB of RAM disappearing somewhere. Please help!