As Michael said, without knowing your environment these are just basic recommendations:

 

 

If you have the bandwidth back to the HO I would highly recommend going with all mail servers at that location. With Outlook Anywhere (RPC over HTTPS) and cached mode it make it very easy to go with a central deployment of Exchange. HP, Microsoft, and many other companies have gone this way.

I would also recommend a CCR cluster at the HO so that leaves you with:
3 DCs - 2 DCs might not be enough to handle 7,000 users. (Make them x64 also)
2 EDGE server (optional, but you are going to want to use something for message hygiene)
2 CCR MB servers - Can host 7,000 mailboxes if the uses are light to medium users for the most part. If not then 4 CCR MB servers
2 HUB/CAS servers - Should be able to handle the load of 7,000 users, unless you have heavy mail uses and a lot of automated messages
2 UC & 2 OCS server (optional, but unified communications and OCS servers make communications SO much better!)

Each branch:
>50 users - 1 DC
<50 users - no DC (assuming the network link is stable)

 

If do go with servers at branches you could go with all in one (MBX, HUB, & CAS), unless your branches have hundreds of users.  You will want to enabled LCR on those servers and maybe even SCR back to a HO DR server, that won’t you won’t have to worry about backing up the remote servers.

 

Jason Sherry - http://jasonsherry.org
Technology Strategist, MCSE: M, Microsoft Exchange MVP

 

Hi All:

The current scenario is as mentioned below;

 

# We have Linux mailing Servers at 9 locations with 1 node running at each location and mailboxes on each node.(Total 7000 mailboxes)

# The Server at the HO serves as SMTP gateway as well as MX Server.

# The other nodes don’t have direct Internet Access to send out Emails, however they are connected to the HO thru IP links/VPN.

# The HO Server is also the master LDAP Server.

 

The above solution needs to be migrated to an Exchange Based Solution. Since we are in a process of migration we plan it to move it Exchange 2007 instead of Exchange 2003 to avoid future migration again.

 

We need to provide a Cost Effective + High Availability Solution to the management. This is what we have planned so far as far as the architecture is concerned;

 

# At HO:

Domain Controller (1 No) + Additional Domain Controller (1 No)

Client Access Server + Hub Transport Server (2 No’s)

Mail Box Server (2) connected to a SAN Box.

 

# At one branch office (where we have maximum no of users)

Additional Domain Controller

Client Access Server + Hub Transport Server (1 No)

Mail Box Server (1 No)

 

Rest all the Branch Offices will connect to the HO Directly for their mails.

 

Kindly let me know if we are missing out on any point.

 

Thanks & Regards

Mitul Z