I have a Curve and have no idea how to or if it's even possible to load Thunderbird (Mozilla) e-mail to my phone. I know I can do Outlook etc but I can't find a system or a hack that will allow me to get Thunderbird to work.
Thunderbird is merely an email client program. The BB Messages application is another email client program. You can't get Thunderbird on the BB, but it's very easy to get the address you currently have associated with Thunderbird pushed to the BB. Have you already set up any emails on the device?
