Yahoo has upgraded its free email service to put users in touch with mobile subscribers. The improved platform allows users to exchange text messages with mobile phones and comes as the portal experiments with making its Mail application “a stickier experience”. It offers a trio of contact options including basic email, Web chat and the transmission of text messages to mobile. The text-to-mobile feature is initially available in the US, Canada, India and the Philippines but will expand to a further 21 other markets within next six weeks. Mail users simply type-in a phone number to the email address field to send a text message to wireless friends – although some carriers have already announced they will charge for delivery.