I've read the official sizing document for Client Access Servers, but it and other official documentation seem to suggest the number of CAS boxes is a ratio based on mailbox servers. While I understand this concept, and agree the rule of thumb should work in most enviroments, the problem is that there is an assumption that most people are using Outlook at work,and when they go home or are out of the office will possibly want to connect to Exchange. I'm working on a design for alarge enviroment where I expect many of my permanent users to utilize non-mapi connections to Exchange. I do not believe the above mentioned recommendations will be accurate as they do not anticipate this "front heavy" load. What I need is guidance on the number of HT and CA servers to deploy. Something like: "~6,000 active connections to every CA server." or "~20,000 active smtp connections on a hub transport". I realize nobody wants to give hard numbers because CPU, RAM and other hardware is a variable, but anything providing insight would be better than the blanket rule of ratios. I've used System Center Capacity Planner, but I'm hesitant to trust it as it provides no insight into the logic of the numbers it outputs.

I was emailed this: http://www.microsoft.com/downloads/details.aspx?FamilyID=239666A9-B13C-4AD8-AEDB-3ED4ECBB95C5&displaylang=en This helps, but I also need information for IMAP.

Please try to use "Exchange Load Generator" to capture the testing data which you want It can measure the impact of IMAP and other protocol clients on Exchange server Download: 32 bit http://www.microsoft.com/downloads/details.aspx?familyid=ddec1642-f6e3-4d66-a82f-8d3062c6fa98&displaylang=en&tm 64 bit http://www.microsoft.com/downloads/details.aspx?familyid=0fdb6f14-1e42-4165-bb17-96c83916c3ec&displaylang=en&tm Related Tech Article: Microsoft Exchange Load Generator http://technet.microsoft.com/en-us/library/bb508893(EXCHG.80).aspx

I've seen this and plan to use it, but is there no way to get a general recommendation BEFORE I purchase any hardware?

After further searching, I didn't find other hard data for IMAP except that official info you've already found. Still, found a related link which content includes the consideration and sizing for your planning and hope itll help you Planning for Exchange Server 2007 CAS http://www.microsoft.com/downloads/details.aspx?FamilyId=03A684BF-69B8-4354-BD9E-D9D50856EF23&displaylang=en

I appreciate all your help, and while Microsoft hasn't released any real usable numbers, I'll just make an estimation based on the pop3 data and adjust as I go along. Thanks for your efforts!