A couple of questions from a newbie...

I'm planning to get a dedicated server and transfer my domain account from a shared server. Email service is being served by a third party to 200 users. I would like to achieve two things:

1. Minimize the amount of downtime for my email users.

2. Notify the 200 email users with an accurate time frame of when the service will be down.

Can someone lay out the most efficient process I should use when setting up the new server in order to achieve #1? I know I need to somehow change the MX record to point to the third party email service.

How do I determine the downtime window? At what point in the process will my email users experience downtime?

Thanks!

Your user do not have to experience any downtime. I assume you are going to create the mail accounts for the 3rd party vendor in advance. If so, about 48 hours before you are ready to switch, drop the TTL for the MX records to something like 120 seconds. When you are ready, make the change. Not all ISPs honor a low TTL, but it won't matter, for a period of about 6 hours, some people will be sending mail to the old server (don't delete those accounts right away :)), but most people will start sending mail to the new server within 5 minutes.

Let your users know that about 24 hours after the change has been made they should check mail on the old server one last time (make it easy by creating an A record: oldmail.domain.com pointing to that server's IP Address) to get any stray messages, then you can cancel the account.

No downtime, no bounced mail, everyone is happy :)

Thanks!