[@robkk Moderator 10 years, 11 months ago]

@balmfoc48

As the user above states some hosts have a limit of emails that are able to be sent out.

Install this plugin to fix possibly part of the issue. The code used in the plugin will probably be used in a future version of bbPress.

https://wordpress.org/plugins/asyncronous-bbpress-subscriptions/

You may need to also look into asking your server support to increase the email limit if your emails sent grow significantly or use a service like sendgrid or mandrill.