Googlemail to become Gmail in UK
By kris on May 05, 2010.
A five year trademark dispute meant that Google was not allowed to use the name Gmail in the UK. In 2005 a company called Independent International Investment Research claimed it had used "Gmail" first.
Google claimed at the time that the settlement IIR asked for was "exorbitant" and dropped the name. Within a year of launching the free e-mail service in the UK, Gmail became Google Mail.
For more info on this please read more here at BBC Technology - Gmail