Triggers/ redirect actions or hook_user_insert based redirects silently block notification emails

I am trying to redirect users after registration to another page. I have tried User triggers ( with redirect actions ) and implementing hook_user_form_alter to set up a submit handler to set $form_state['redirect'].

Both methods work, they do the redirect - but the notifications do not get sent. In my case a validation email. Am I doing something wrong? Has anyone else seen this behaviour or is it a bug?

Removing the redirects - immediately restores the mail sending. Does anyone have any ideas?