Send email in HTML on WordPress
Wordfence is blocking you from sending mails with JS and CSS.
Some requests contain data that may match patterns the firewall Wordfence uses to detect attacks.
Go to your Wordfence extension menu in &quot;All Options&quot;.
In this page go to the Basic FireWall Options part and activate the &quot;Learning Mode&quot;.
Verify in the Advanced FireWall Options that all the rules are activated.
Add your request in Allowlisted Urls.
Don't forget to Save changes when you are done.