Check it out: http://www.google.com/search?hl=en&lr=&q=http://gmail.google.com/&btnG=Search http://www.google.com/search?hl=en&lr=&q=http://gmail.com/&btnG=Search
gmail.google.com redirects to http://www.google.com/accounts/ or http://mail.google.com/mail/ depending if you are logged in or not. Update: Plus, they are in the index... [search=google]site:gmail.google.com[/search]
What I find strange though, is that the gmail.google.com page pops up for a search result, but when querying it directly. it show up as not indexed: http://www.google.com/search?hl=en&q=gmail+login&btnG=Google+Search http://www.google.com/search?hl=en&lr=&q=gmail.google.com/&btnG=Search
Until recently, Google would index urls that are redirecting as well as the urls that were being redirected to as long as there were a lot of incoming links to support the site. Gmail and it's urls definitely have that. Now I am seeing a trend that eliminates the unnecessary urls. Seems like they want to set an example with their own as well