So I am getting this error for more than 30 minutes now whenever Wordpress try to send email.
https://status.mxroute.com says “Experiencing issues” but there is no detail.
Are we having issues with friday.mxlogin.com?
Either the connection is blocked on the side of your firewall or provider, or your server’s IP is blocked on the Friday server: https://unblock.mxrouteapps.com
The issue was caused by plugin conflict. I deactivated the plugin and now it is working fine.