Today I actually exhausted my 2699 MB of Gmail account!
And discovered that
"Don't throw anything away.
Over 2699.927722 megabytes (and counting) of free storage so you'll never need to delete another message."
Actually is not true.
Once I exhausted my email space, mails started bouncing and to my surprise Gmail also takes into account trash folder messages while calculating the actual space consumed.
Once I deleted mails from Trash Can, all was back to normal.
Strange…. is the world