what is architecture of gmail application and what are the non-functional attributes of gmail?

The guy/gal asked a good question and glad that you posted it here.. :)

Read the post here:
http://css.dzone.com/news/gmail-architecture-part-1

You could do this to check the services list. The services will tell you a lot about its architecture.
- Download "fiddler"
- Run Fiddler in IE (any version)
- Open Gmail in another IE window
- Look at the services calls and traffic
- Login to your Gmail account or try creating one while still keeping an eye on the traffic in Fiddler
- try sending/reading emails, or even create few labels..