After my domain and hosting were transferred to another hosting company, some emails were not received by my mail accounts which are using G Suite as mail server.
Sender received this email after the sending email was bounced back.
The response was:
550 Please turn on SMTP Authentication in your mail client.
mail-it0-f50.google.com [209.85.214.50]:53804 is not
permitted to relay through this server without authentication.
I have configured the MX record, and the emails are up and running. However some emails are not received by us. I am wondering if this issue is related to us (maybe SPF record) or to the sender?