Quicklink: Mobility Email
Mobility Email is a device-independet mobile email solution. At the core of Mobility Email is Mozilla Thunderbird, the wildly popular open source email client. It's loaded with extensions to provide OpenPGP encryption and signing, access to Hotmail, Yahoo!, Lycos and MailDotCom email accounts, and a way to quickly access your contacts.
Mobility Email is free. It's open source. Check it out here.