Automatic followup email plugin not finding the siteurl

Hi,

I've just installed the automessage plugin for scheduled emails. The emails are going out but the unsubscribe footer text shows the follow:

To stop receiving messages from xxxxx Blogs click on the following link: http://unsubscribe/de2cb86129e7d2eee6247ca989a7bdff

It's not figuring out %siteurl% which appears to be set by this line:

$replacements['/%siteurl%/'] = 'http://' . $site->domain . $site->path;

This is on a sub-domain install.

Thanks for your help
Joss