It now fails gracefully, but really I'd like to be able to disable that subject bar altogether instead of letting users change it only to be told off.
$subject: subject of the mail
$text: text of the mail
+'EmailUserPermissionsErrors': to retrieve permissions errors for emailing a user.
+$user: The user who is trying to email another user.
+$editToken: The user's edit token.
+&$hookErr: Out-param for the error. Passed as the parameters to OutputPage::showErrorPage.
+
'FetchChangesList': When fetching the ChangesList derivative for a particular user
&$user: User the list is being fetched for
&$skin: Skin object to be used with the list