You can send text messages to any text-capable T-Mobile phone number using your phone's text messaging app. T-Mobile supports standard SMS messaging protocols, so any SMS-compliant phone can send messages to or receive messages from a T-Mobile phone.
SMS messages are limited to 160 characters per message, and there may be restrictions on the number of messages that a user can send in a billing cycle or on sending messages to international numbers. These restrictions depend on the service plan that the user has on her T-Mobile device. T-Mobile also does not store copies of SMS messages, so it is not possible to retrieve deleted messages.