I am having exactly the same problem, however, although I get the error message, the email is sent out to the subscriber. Subscribe2 is also successfully sending emails to subscribers to notify them of new posts etc. It’s only when you do a subscription that there is an error message.
I have the latest vesion of the plugin (4.13) and WordPress version 2.7.
Any bright ideas? I really need to resolve this before I publicise the blog to all of the users of my software! Thanks.
