i.e. user logs in then goes to > dashboard > email notifications > set to instant notification
also do you receive registration emails and any messages sent through the mass mailer in admin?
could be that you host does not allow php scripts to send out emails, you could try contacting your host also
when did you last update it?
@Mark, do you have any other suggestions? How can I have someone look at this for me?
if in the admin and in debug/dev mode it shows its still version 2.6.1 then something is wrong.
when did you last update it?