Be sure you do email verification before users are able to post. Block domains of temporary email services (there are lists floating around GitHub, Google is yo

Be sure you do email verification before users are able to post. Block domains of temporary email services (there are lists floating around GitHub, Google is your friend). Only allow one account per address. Figure out what domains the spammer is using to make email accounts. If you can, block them entirely, if not, require manual approval just for those domains. Use the other suggested technoques, like shadowbanning etc. Consider requiring or allowing social log in or phone number verification.