Currently the server can handle around 450 received and 350 send emails an hour based on the statistics from:
Main >> Email >> View Mail Statistics

The remaining emails are put in queue and can take between 1 and 10 minutes to process.

The server is a
Intel Xeon 3040 (dual-core 1,86 ghz)
4GB DDR2 Ram
2x80GB HDD (64% free)
Serverload during peak times is around 0.80 to 1.40


Is the anyway to increase the number of emails the server can handle by tweaking cPanel/Exim?