Mandatory SMTP Authentication is now required.
When Simple Mail Transfer Protocol (SMTP) designed at early stage, it do not provide any real verification for sender.
A mail server that do not verify those sender detail is an Open Mail Relay which allow anyone on the internet to mail over any destination.
All JS-Solutions shared hosting mail servers require email user tick to turn on SMTP authentication in their email client and we will force it start from 1st Sept 2018.
This implementation is purposely designed for strengthening the security level and prevent trespassing from unauthorize party.