If you have a Google App account, you will be able to connect to GTalk using your custom domain name. In Linux, you can connect to your Google Apps GTalk account using your favorite IM client too. It is very easy to do it. The trick lies in the configuration. Once you got it correct, it will work everywhere.
In Empathy, all you have to do is to add a new GTalk account, enter your Google Apps username (together with your custom domain) and password and click Login. That’s it.
In Pidgin, go to “Add Account” section and select “Google Talk” from the Protocol dropdown field. Enter your username (without the domain), the custom domain for the Google Apps and the Password.
Next, click the “Advanced” tab and enter “talk.google.com” in the “Connect server:” field.
There are more steps required to configure Google Apps Gtalk for Kopete. First go to the “Add Accounts” section and select “Jabber”.
Enter your Google Apps username and password.
Go to the “Connection” tab. Check the top 3 boxes (Use SSL, Allow plain text authentication and override server information) and enter “talk.google.com” into the “Server” field.
Click Next and “Connect Now”. That’s it.
The above are the instructions for the three major IM clients used in most Linux distro. For other IM clients, as long as they support the Jabber or XMPP protocol, you will be able to setup your Google Apps Gtalk account using the settings above. Let us know if you have any question or difficulty connecting to your Google Apps account.