Please check out Client was not authenticated to send anonymous mail through Office 365 for the latest information on this topic.
Suddenly, i got this message while testing through OUTLOOK 2007 :
"Send test e-mail message: Cannot send the message. Verify the e-mail address in your account properties. The server responded: 530 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM [MA1PR01CA0099.INDPRD01.PROD.OUTLOOK.COM]"
Everything is working fine earlier and no changes were made on our side and also have configured my DNS txt record, changed login password but still nothing happens.
I would appreciate if someone could help me on this.