Our MX record was setup at the wrong office years ago. We have a route setup to port the e-mail to our Exchange Server at the corporate office. I'm going to add a new MX record at our main office where the Exchange server is located. I spoke with the company hosting our ISP and with the company who makes our e-mail filter. They suggest the setup below. What do you think?
Setup new MX Record called Mail1 at corporate office with priority of 3. Current MX record at remote office has priority of 4.
In the slim chance I've made a mistake and this doesn't work, how long does it take to failover back to the old MX with priority 4?
If there was an issue with Priority 3 MX, i fix it, then how long does it take to fail back from Priority 4 MX?
I spoke to the company hosting our MX record. They told me all of this was instant. I find that hard to believe and look forward to your input.