spam
- http://www.mail-tester.com/
- https://glockapps.com/
- https://www.mailchannels.com – used by hosting providers to stop outgoing spam.
- DMARC
- grscripts.com – ASSP based plugin for cpanel to stop spam.
- https://mxtoolbox.com/blacklists.aspx – check if IP black listed.
- https://rspamd.com – Bayesian based spam filter. Similar to Spamassassin
Link Spam
Captcha
https://www.hcaptcha.com