We are upgrading from a Windows 2000 server to a Windows 2003 server. We are also adding Exchange 2003 and bringing e-mail in-house. We are considering bringing the Web hosting in-house also. Currently we have over 150 e-mail accounts, but only around 40 of them will be using the functionality of Exchange. We are using a "cheapy" Web/e-mail host for our needs right now. When we upgrade, how can we keep that number of e-mail accounts on the same domain without having over 150 Exchange licenses? Is there a way to continue using our "cheapy" host for the accounts that do not need the Exchange functionality and still keep the same domain name across the board?
Good questions. To answer the first question, if you establish a total of 150 mailboxes on your soon-to-be internal Exchange infrastructure, then these users will be able to access Exchange Server either through MAPI clients such as Microsoft Outlook or through HTTP/HTTPS clients such as Outlook Web Access. So you won't end up exceeding your 150 Exchange licenses.
In answer to your second question, yes, this should be possible. Basically what you'd need to do (test all this in a lab first) is:
- Set up the 40 users on your Exchange 2003 infrastructure.
- Configure Exchange 2003 to accept all e-mail inbound to YOURCOMPANY.COM.
- Configure Exchange 2003 to "send unresolved messages to a smart host," where the smart host is the external IP address of your hosting provider's SMTP gateway (i.e., the equivalent of where your public DNS Mail Exchanger [MX] record is pointing today)
- Redirect your public DNS MX record to point to your Exchange environment (i.e., whatever IP address[es] you have opened on your firewall for port 25 in order to route mail through to your Exchange 2003 environment).
Once you set up this infrastructure, Exchange 2003 will accept all mail destined for YOURCOMPANY.COM and then check locally to see if the target mailbox is hosted on Exchange (i.e., those 40 mailboxes). If the SMTP message is destined for an Exchange mailbox, then the message will be delivered locally. Otherwise the SMTP message will be routed to your hosting provider's gateway for delivery to the "cheapy" Web mailboxes.
One final note: Make sure that your reply-to addresses throughout both the new and "cheapy" environments are all set to YOURCOMPANY.COM. The "cheapy" environment should be set that way already, but the new environment you set up will need to be configured this way as well, obviously.
Hope that helps!