My Q&A plugin will not send users emails

Hi, I purchased Q&A and have been testing it because it will not send my registering users their passwords. I've tried deactivating other plugins, did not work.

I tried registering users through my site.com/wp-admin which worked smoothly, they got the email in seconds. This suggests that there is something wrong with the plugin and I would appreciate it if you could sort it out please.

My domain name is startsmarter.co.uk.

Oz