order to receive calls, however, the user had to upgrade to a full Google Voice account. Initially, users outside of the US could not upgrade to a full Google Voice account or receive phone calls in Gmail. (Outbound calling through Gmail did not require Google Voice and was available in many countries outside the US.) Google Talk allowed users to leave a voicemail for a contact whether or not they were signed into Google Talk. Messages could be up to 10 minutes long and users could choose to have them sent to their Gmail inbox. Messages could be sent with or without first ringing the recipient's phone number. Google also provided a Voice and Video Chat browser plugin for Google Talk (not to be confused with the standalone Google Talk client) that supported voice and video chat between Gmail users. The plugin was available for Windows (XP, Vista, and 7), Mac OS X (only on Intel-based Macs), and Linux (Debian, Ubuntu, Fedora, and OpenSUSE packages available, but the binaries worked on other systems). The plugin had to be downloaded and installed, but otherwise seamlessly integrated into the Gmail interface. Encryption The connection between the Google Talk client and the Google Talk server was encrypted, except when using Gmail's chat over HTTP, a federated network that didn't support encryption, or when using a proxy like IMLogic. End-to-end messages were unencrypted. Some XMPP clients natively supported encryption with Google Talk's servers. It was possible to have end-to-end encryption over the Google Talk network using OTR (off-the-record) encryption using other chat clients like Adium (for Mac) or Pidgin (for Linux and Windows). Google's version of "Off the Record" was not OTR (off-the-record) encryption. Enabling "off the record" inside Gmail's Chat turned off logging of messages, but did not enable encryption. Offline messaging On November 1, 2006, Google introduced offline messaging to Google Talk. This allowed users to send messages to their contacts, even if they were not signed in. They would receive the messages when they next went online even if the user who had sent it was offline. This only worked between Gmail-accounts, not between Google Talk servers and other XMPP servers. Mobile device compatibility On June 30, 2006, Nokia released new software for their Nokia 770 Internet Tablet, that included Google Talk as one of the compatible VoIP clients, because of the XMPP-based software. Another Google Talk-compatible device was Sony's mylo,