XF 1.2 New users not receiving confirmation emails

I wonder if someone can help, for some strange reason new users are not receiving confirmation emails when they register. I am currently on v1.2.3. This wasn't a problem before the upgrade.

Does anyone have any ideas what could be the issue?
Hi Jeremy.

I used a test account myself and haven't received any emails, nothing is caught in the junk folder. There are no error logs that I can see. How would I check if emails are being sent from the server?

This never used to be an issue before 1.2.3 - so not sure what has caused this conflict.