I just installed Joomla 3.6. I have the latest version of CB.
When users sign up for access to my website, they have to confirm their emails by responding to an email sent by my website to their registration email.
My users are complaining that they are not receiving emails. This website is 10 years old. I have been able to send emails in the past.
I am using SMTP to send emails. I can send emails using the same SMTP settings from gmail.com . So my settings are correct.
The problem seems to be Joomla and possibly CB.