Q-Mail Max Rcpt Patch allows you to set a limit on how many recipients are specified for any one email message. RFC 2821 section 18.104.22.168 says that an MTA must allow at least 100 recipients for each message, but may elect not to allow any more than that. Choosing to enforce this limit can help mitigate damage from one of the favorite tricks of the spammer.
RetinaPost is a PHP class/WP plugin that makes CAPTCHA's clean and engaging using feeds or custom text. It is easy and intuitive for your Web site visitors. You can choose to use your feed or custom text to inform or guide the user to read more articles or to perform other actions. Use RetinaPost to stop spam and bots on forms, on comment posts, new account registrations, polls and surveys, and more.