You learn when installing MailScanner that more RAM is good. And if you find that you can actually AFFORD to fully populate your (32-bit) motherboard with RAM you can stick up to 4 Gigabytes in there. HOWEVER, your system will not take advantage of all that RAM if you’re not using a HIGHMEM enabled kernel. If you see something like this in dmesg (or if you’re quick, in the messages that fly by when you boot):
Warning only 896MB will be used.
Use a HIGHMEM enabled kernel.
896MB LOWMEM available
then the kernel you’re using IS NOT HIGHMEM enabled. (Duh.)
One choice would be to configure and compile your own kernel. If you’re loathe to do that, in Debian at least, the SMP (Symmetrical Multi-Processing) kernels will work on single-CPU machines and they have HIGHMEM enabled by default. Easy.