Changing email hosting

The MX record in a domain’s DNS zone:

silver-stage.com.        IN      MX  10   mail.silver-stage.com

tells computers around the internet where to deliver email so it arrives on your mail server so you can collect it or view it at your workstation.

An A record in a domain’s DNS zone:

Mail      IN         A          213.175.222.24

Determines the physical location of a host (in this example your mail server).

When you change your email hosting, the IP address (4 groups of numbers above) will need to change in the global DNS infrastructure. Although the propagation is prompt, any change you make to a DNS zone will not be echoed around the globe instantly. This means that with a constant stream of emails heading to you from around the world at the instant of change over – some email will go to the new email server and the rest will go to the old one!

The solution! If you are to not lose any email you must obviously first ensure your new mail server is behaving (we regularly use test domains aliased or parked on a server) and again obviously configure the mailboxes you want to transfer on the new host. The trick is to leave the old server live for 24 hours (these days you could probably get away with 4 hours unless you use an obscure TLD) and then point your clients (in your case I believe you’re still running using googlemail) at the old mail server’s IP address 213.175.222.24 to mop up any email that was delivered to the old server, remove the connector to the old mail servers IP address and only then – decommission the old mail server. If you being really precious about it – you could even double check that the old mailboxes really were empty before decommissioning.