We are moving one of our smtp servers from one hosting provider (A) to another hosting provider (B). Because of this move, the IP address of the server will have to change.
Our plan is to do the following:
- Build clone system at new facility.
- Register reverse-dns for new ip ( owned by provider B) address to mail.company.com
- Change forward DNS TTL for mail.company.com down to an hour.
- Leave things be for three days (Assuming that's how long it would take for the cached records expire / drop off cache) RE: What percentage of nameservers honor TTL these days?
- Change forward DNS for mail.company.com to point to provider B's ip address for new system. (plus raise TTL back to 24 hours)
- Turn off system at provider's A site a week or so later.
Is this a reasonable plan? Is there anything we can do to minimize the outage for sending and receiving mail? One of the concerns I had for sending email out were those systems that use reverse dns and forward dns to validate that the machine was on the up and up. I thought incoming mail was less of a problem. Am I missing anything in the process?