I've just done a clean install of 2.0.17 and I'm configuring boards and testing stuff out.
I have email set on the php default.
I set registration with email activation and registered a test account but no email was received. There was nothing in spam and nothing in the error log.
I changed registration to Admin approval and tried again. User received an email to say the request has been created and is waiting for admin approval.
In the admin center I selected 'approve with email validation' but no further email was recieved, no spam, no error log.
Any ideas why some emails get through but activation/validation emails don't?
UPDATE:
Maybe I was expecting too much? Tried again from scratch and the activation email was received 50 minutes after registration. Is that normal?