Prepared an email to send as I have done many times before, this time when I pressed send the spinning circle beside the iPad signature kept spinning and there was no whistle sound indicating it had been sent. So I assumed my wifi connection had been lost, so I shut down my ipad [slide to power off] so my ipad would reboot the wifi connection when it turned on again which it did, but my prepared email to be sent was gone. What happened and how can I prevent this from happening again ??