I have been receiving this error message for two days. I have made no changes to my email client.... anyone else in this situation? Used personal email address to contact support but no reply.
Unable to send message;Reason:550-Please turn on SMTP Authentication in your mail client, or login to the550-IMAP/POP3 server before sending your message. sender1.zohomail.com550-(mail.zoho.com) [74.201.84.157]:52940 is not permitted to relay through550 this server without authentication.