Continued. Your ISP will be able to tell you what settings to use on your gateway or router
Hi — I (Wrobinson) am going to add a bit more here, as I have some experience with this.
Since you will be shutting down the Exchange server in order to move it to the new location, mail will temporarily be undeliverable. Sending servers are usually configured to retry failed attempts every so often; however, this is a configurable setting and there is no guarantee as to how it is set for any given sending server. To guard against missed messages, you will want to request a “mail bag” from your new ISP. What this means is that mail destined for your Exchange server will be held and queued at the ISP until the server is back online at which time it will be delivered. This may cost a little extra, but since you are a new customer, they are more than likely to kick it in for free as a value added service.
To set this up, you will need to — or have the ISP configure the MX records for your domain to point to their mail environment with a higher priority than your own MX records. Once the move is completed, the additional MX record can and should be removed unless you plan to maintain this as a monthly service, if available.