On Thu, 29 May 2003, Tony Hain wrote: > Dave Crocker wrote: > > Please indicate some historical basis for moving an installed > > base of users on this kind of scale and for this kind of reason. > > their customers about the opportunity to use a new app. The larger > providers (AOL, MSN, Yahoo, ...) can drive media attention and might The providers you have listed all have what I'd call closed applications. Yahoo is (largely) browser based working from a MUA coded in their server. AOL is client-server, again the MUA is in their server and, I believe but have never observed, MSN is similar to AOL. Other examples as well. Once a new/updated mail protocol is available, then each of the above must implement updates to their servers. Then deploy the changes. The new revised system will just happen to the average user of those services. The slower process will be the millions of smaller mail infrastructures, As long as the new protocols provide a migration plan and support, upgrade over a year or two is a reasonable expectation. A key requirement on the providers of the server and client software is to NOT include dependancies on related system software versions which would force the prospective upgradee to encounter the upgrade domino chain which ends up in substantial costs for unrelated software or hardware. Dave Morris