One of my customers has a Intel C2 E4400 server with 2 Gigs of RAM and is hosting around 50 websites, the majority of which are PHP and MySQL based. He has a user base of 1 million to whom he has to send newsletters every fortnight. The current server is not capable to handle the load of 2 million emails every month. What is the best recommended configuration for these kinds of requirements? In the current config, what should be the amount of emails to be sent at a time?
