In order to prevent spam users, bots, and users with unusual emails from registering in Ultimate Membership Pro we can suggest the following measures:
- Use Double Email Verification, spam users will usually be unable to verify their registration since the emails are fake, and you can set it so they will be deleted after a period of time without verification.
- Use the Blacklist Disposable Emails add-on, which allows you to prohibit registration for disposable or suspect email domains.
- Use the Email Address Black List settings in General Options > Security