You can disable Activity notifications plugins in the admin panel to not have any notifications, but in this case you won't have on-site notifications as well. 

Or you can set all users default value to "Never" for sending e-mail notifications, this has been discussed previously, please do the search on the fourm. 

As to the signing up, you can disable verify e-mail option in the admin panel as well
Now you left only with the welcome letterYou got two options there: 

1. do modifications of the codein ow_system_plugins/base/classes/event_handler.php 
line 1451 the method
    public function onUserRegisterWelcomeLetter

2. option is to enable smtp and do not configure it. But in this case all welcome letters will pile in the database. 

Don't forget to remove forgot password link from your site as well, as it sends e-mail too. 

Why do you need this anyway? 

Thank you for answering
Yes i need ( set all users default value to "Never" for sending e-mail notifications) but i can't find the method here :(
I need to do this because i have a lot of members they have the incorrect emails (i turn off users verify email), and when the email notifications sends the load of cpu will be high

Thank you

Topic was moved from General Questions.

How can we Hide the Oxwall Option to Subscribe To Newsletter?  :--) 

im having trouble removing intergrated codes of Music Extre,My File Manager,Games,Message All,& Reminder Notifications,ive uninstalled them all however the intergrated codes remain,need help will pay to remove what do you charge for this?

Email me @ sugarjohnny80@gmail.com