It's frustrating when you get an error after sending an email message. This article describes what you can do if you see error code 550 5.7.515 in a non-delivery report (also known as an NDR, bounce message, delivery status notification, or DSN) when you try to send email to Outlook.com and related Microsoft consumer email services (Hotmail, Live.com, MSN, etc.).
The full error is:
550 5.7.515 Access denied, sending domain <domain> does not meet the required authentication level.
The sender's domain in the 5322.From address doesn't meet the authentication requirements defined for the sender.
Use the information in the NDR to help you fix the problem.