The Sender ID is the mobile number that is displayed on the recipient's cell phone. It's possible to reply to that number by hitting the reply-to button.
My-Cool-SMS supports numeric Sender ID and let's you receive replies directly to your mobile. The EXECUTIVE account also includes text sender id, which can be a company or any word with up to 11 characters.
Please note that the Sender ID feature is currently *not* available when sending to the following countries: China, Malaysia, Mexico, South Africa. When sending SMS to these countries a random number will be displayed on the target handset instead.