How to Disable User Registration in Joomla 3.10
Depending on the version of Joomla! that your website uses. the default settings might allow users to register and create new accounts within your website. This can be a problem especially if you do not have reCaptcha activated. Spambots will take advantage of this opportunity and fill in the user registration form which can result in hundreds or thousands of automated emails being sent from your server to these fake emails. If your website sends too many emails in a short space of time, your web host might turn off your email sending capabilities to protect themselves and other users.