Looks like a configuration error from your side “'Please turn on SMTP Authentication in your mail client” Just enable the authentication and it should work Regards Alex From: geoffrey gitagia via skunkworks [mailto:skunkworks@lists.my.co.ke] Sent: Monday, November 27, 2017 4:22 PM To: Skunkworks List <skunkworks@lists.my.co.ke> Cc: geoffrey gitagia <ggitagia@gmail.com> Subject: [Skunkworks] Safricom Emails Hi Guys Anyone else affected by the below error ---------- Forwarded message ---------- From: Mail Delivery System <MAILER-DAEMON@rat01.safaricombusiness.co.ke <mailto:MAILER-DAEMON@rat01.safaricombusiness.co.ke> > Date: Mon, Nov 27, 2017 at 3:47 PM Subject: Delivery Status Notification (Failure) To: ggitagia@gmail.com <mailto:ggitagia@gmail.com> The following message to <XXXXX@XXXXXXXXcom> was undeliverable. The reason for the problem: 5.1.0 - Unknown address error 550-'Please turn on SMTP Authentication in your mail client. \n(rat01.safaricombusiness.co.ke <http://rat01.safaricombusiness.co.ke/> ) [197.248.254.120]:42090 is not permitted to\nrelay through this server without authentication.' Final-Recipient: rfc822;XXXXX@XXXXXXXXcom Action: failed Status: 5.0.0 (permanent failure) Remote-MTA: dns; [197.248.5.12] Diagnostic-Code: smtp; 5.1.0 - Unknown address error 550-'Please turn on SMTP Authentication in your mail client. \n(rat01.safaricombusiness.co.ke <http://rat01.safaricombusiness.co.ke/> ) [197.248.254.120]:42090 is not permitted to\nrelay through this server without authentication.' (delivery attempts: 0) -- GG