Question : How many emails can we send?

We are a paperless (email only) billing company with many (120,000+) email recipients.  We are trying to get a handle on our capacity to send emails and were hoping to get some insight from this board.  

We have normal internal user traffic for most of the month, but on the 1st of every month we send out a huge amount of emails from one "from" address.  We would like to know how we can determine what the theoretical "best practice" maximum number of emails we can send through our single Exchange Server 2007 device.  We have a Dell PowerEdge 2970 with 2-Quad core 2.2 GHz procs with 6GB of RAM.  

All of the sizing examples I have found tell you the size of server you should purchase depending on your load.  But this is the reverse of that and we are also not sure if the "bulk" email nature of this process is taken into account.  

If you could tell me how to figure this our or at least point me in the right direction, I would be much obliged.

Thanks for your help.

Answer : How many emails can we send?

Since your traffic and routing equipment not to mention potential other resources being drained on your server are unique to your office the only way to get a real idea is to perform some benchmarks.

There are some straight forward tools included in Windows Server (Performance Monitoring) that you can setup, or you can purchase software for this.

I would start with Performance Monitor and set it to watch Network Bandwidth, Memory Usage, Hard Disk usage, and processor's. You will need to do this on a day that would be "slow" for traffic, medium and then on the 1st which you say is the most load. The first two measures are just to give you an idea of how your server is performing on the heavy day compared to a light day.

Example: Let's say on the 1st you send out 5 million emails all at once, the server ques them up and you see the hard drive speed max out, processor at 100% and memory fully used for the entire duration of the email sending. Now cut that back to say 4 million emails all at once and compare the results, this will help you determine the max amount of emails at one time your server can handle. You also need to take into account the results from the light day (say 5,000 emails sent and server load is 90% for 2 minutes) you can compare these to determine that at 3 million emails your load will be 100% for x minutes (approximately)

This is just benchmark your single email server, if you want to see how this effects the rest of your network you will need to monitor routers, users PC's, and perhaps even your ISP and your other internal resources.

Also check out the Exchange stress test tool from Microsoft (Exchange load generator in left column half way down) http://technet.microsoft.com/en-us/exchange/bb330849.aspx