@nothingman, perhaps you could try running a similar test to Gibby? Upload a separate mail test first and see if that works.
At the moment, this is the change I'll be making in Hotaru 1.1.4 due the first weekend in April:
/libs/EmailFunctions.php lines 102-104:
I've left $return_path in there, but set it to blank. Gibby, could I bother you one more time to test the above code? Thanks.
//$return_path = "-f " . SITE_EMAIL;
$return_path = "";
mail($this->to, $this->subject, $this->body, $this->headers, $return_path);
@Alf, how about you? Any progress at your end?