mattglet - 2:54 pm on Aug 13, 2004 (gmt 0)

You have to look at the numbers. How is your CPU usage looking? How is your database memory usage? How many emails are being sent per day?

In a perfect world, you should definitely have each section of your site (web, database, email) on different servers. Email is one area that people tend to underestimate. If you're sending out a lot of batch emails, it can cripple a web server (especially with inefficient code). At the very minimum, you should have at least 2 servers (web & database).