Well, as the title says, in the version 13 of Mail Client de Mozilla we will have the option of using instant messaging integrated into the same interface.
Apparently the integration will be achieved using the project Instantbird, the multiprotocol instant messaging client of Mozilla. Instantbird currently support the protocols AIM, Facebook Chat, Gadu-Gadu, Google Talk, Groupwise, ICQ, IRC, MSN, MySpaceIM, Netsoul, QQ, Simple, Twitter, XMPP, Yahoo y Yahoo JAPAN. Plugins with additional protocols such as accessories.
As far as I understand, the option to use the IM Client is optional, and the notifications of new messages will not be intrusive when we are working with the Mail Client. As announced Gary Kwong on his blog, we will be able to test this functionality starting tomorrow in the version Nightly which confirms that the new version of Thunderbird should leave today 😀