https://github.com/martignoni/hugo-cloak-email
http://www.anti-abuse.org/multi-rbl-check/
https://www.rescam.org/
http://www.mail-tester.com/
https://www.ne-m-appelez-plus.be/
http://www.allaboutspam.com/
http://www.webdesignfromscratch.com/javascript/human-form-validation-check-trick/
http://techblog.tilllate.com/2008/07/20/ten-methods-to-obfuscate-e-mail-addresses-compared/
http://www.phpcaptcha.org/
http://www.robinsonlist.be/