A bug has been found in Articles v0.12 that prevents the e-mail to friend feature from working.
The next release of Articles will use the XOOPS built-in e-mail functions, so it will be fixed for that.
In the meantime, fixing the current version is a simple task: Open "email.php" in your favourite text editor and uncomment line 196 (remove the "#") and re-upload to your web space.
If the archive you have downloaded is articles_0.12c.*, then this has had the file modified already.
Apologies for this silly mistake!