Based on information found buried deep within the GMail's javascript source, Garett Rogers in a post at ZDNet entitled "GMail code hints at coming domain feature" gives a pretty good hint that Google is developing a service that will make GMail as a server. The code name of this service is "Caribou".

What makes Garett Rogers say that is these portions of javascript code from GMail:

function vJ(){if(uy){;return'<a class=lc target=_blank href="'+ry+
'">'+"Manage this domain"+" | "}else{return""}}}

AND
var kQ=ob(["Contact us …","Report bug","Caribou is slow","Send a 
suggestion","I need personal help!","Caribou-only features"],5);

To read the full article: http://blogs.zdnet.com/Google/?p=95