Banister, I did a new installation of UNA, and had forgotten all the configuration stuff from my prior installs.  Anyway, I encountered the same problem.  I resolved it when I noticed in the Studio > Settings Module > Cache > "Email to send site messages from" that it required the email to send site messages from as no-reply@mysite.com email.

It appeared that the SMTP Mailer module was in conflict with this already set email setting in the Settings Module.  I was not getting the site to send out confirmation emails until I removed the SMTP module.  Then it worked, I sent a confirmation email to myself from a profile I created.

It might be possible to remove the email from the Settings Module, in order to use the SMTP module, I have not tried that yet.  However, this worked for me, so you might try it.