jamiechong

A lot of registration spam comes from emails with a subdomain. Spammers control a domain such as buymyjunk.com and then attempt to register on your site with emails such as irenemwd@foster2.buymyjunk.com and jakemgm@foster7.buymyjunk.com. This plugin simply blocks all registrations using a subdomain.
Reputable users will have a normal email address from a reasonable domain like @gmail.com, @mylegitbusiness.com, @outlook.com, @myschool.edu, etc.
There is no configuration and no setup. It simply just works. The plugin logs all blocked registrations so you can find potential false-positives. Find a link to this log file on the Plugins page where you activate/deactivate this plugin.

Ban Subdomain Emails

Prevent people from registering with emails that contain a subdomain to help reduce spam.

Hudson Atwell

Use this plugin to automatically detect and remove bbPress replies marked as spam from the database.
This plugin was developed to help improve database optimization.
<h4>About the Plugin</h4>
http://youtu.be/G2AEf5VEGIk

bbPress: Auto Delete Spam Replies

Automatically delete bbPress spam replies older than X days.

Ban Subdomain Emails vs bbPress: Auto Delete Spam Replies