As a general rule, from the moment you click 'send immediately' it takes approximately 10 seconds for the message to reach the contact's handset.
Within the SMS world there are many factors that can affect how quickly the message is sent. The carrier may be experiencing heavy traffic at the time which will slow down message delivery.
It's also not uncommon for a handset to be switched off or out of range. In this case, our system will attempt to resend your message for 12 hours. However, the message will expire and fail if the handset is not within range or switched back on during this 12 hour time period.
All messages, taking into account these factors, should be received by the handset within 10 minutes of the message being sent out. If you are experiencing delays longer then this please drop us a line so we can check things out for you.