I need a new server for exchange 2007, it'll have about 70 mailboxes. We prefer Dell (all our servers are Dell). How can I tell what kind of specs the server will require?
There is a Exchange 2007 Mailbox Server Role Storage Requirements Calculator spreadsheet available here. A blog post that explains how to use it and everything that is factored in is available here. The calculator uses all the recommendations outlined in the following articles:
Planning Storage Configurations - http://technet.microsoft.com/en-us/library/bb124518.aspx
Planning Memory Configurations - http://technet.microsoft.com/en-us/library/bb738124.aspx
Understanding Exchange Server 2007 I/O improvements from 64 bit - http://msexchangeteam.com/archive/2006/09/08/428860.aspx
Also here are the general system requirements.
Exchange 2007 needs some fairly heavy-duty hardware. It also requires a 64-bit OS, so keep that in mind when selecting -- means if buying new you'll need a 64-bit version of Win 2008 Server. I can't really speak to Dell hardware specifically, but for a single-server instance you'll want to hit it with at least 3-4 GB of RAM, and you'll probably want at least 2 way (probably 2 x 2 way or 1 x quad core) CPU at 3 GHz. If you split up the store and the MTA/routing between boxes, you may be able to get away with a little less heavy-duty hardware. HD space itself is fairly cheap, but you'll also want some kind of raid on the hard disks, preferably a hardware controller that's capable of raid 5 or raid 6 but you'll have to pay for it. How much disk space depends on your mailboxes and what else you want the box to do (best answer: nothing).