Migrating Server to Another Box/IP

[J Malcolm]

I am planning to move my domains to another box and another IP address.  I’m well aware of the propagation delays when a domain’s IP address changes.  I need to minimize the disruption to my users and obviously not lose any mail in the process.  Is there any ‘best practices’ for how to do this?   Details:  when I actually throw the switch, some mail will begin going to the new box fairly quickly while some mail from servers using a cached DNS entry for the domain will continue to send to the old box until the cached address expires, which could be a couple of days.   Likewise, some users’ mail program will almost immediately start going to the new box while others may stay on the old box for a couple of days.   So the question is…  is the right answer to just let whatever happens happen for a couple of days, and then when the dust settles reprocess any leftover mail on the old server to get it routed to the new server?  The obvious problem with this is the potential for mail that won’t be seen for couple of days.  Is there a tried and true better way.   Thanks.   Jerry