For the sake of saving an hour of guessing, here are the proper settings for using Google Apps, or Gmail, with StatusNet, formally known as Laconica:

$config['mail']['backend'] = 'smtp';
$config['mail']['params'] = array(
'host' => 'smtp.gmail.com',
'port' => 587,
'auth' => true,
'username' => 'username@domain.com',
'password' => 'your_secret_password'
);

Adding these settings to your config.php file will allow your StatusNet instance to send email notifications over SMTP when your web host doesn’t support sending mail from the server (ahem, WebFaction). The trick is to use the proper port, 587 instead of 25, and to enable authentication.

I’m still trying to configure Google Apps as the XMPP provider for StatusNet too; I’ll put together another post if I can figure that out.