530 validating sender
When you're away from home and send an email message using your home email account, your email message might be returned with a 550, 553, or relay-prohibited error message.
The same situation could occur when you're away from your office and try to send an email message using your work email account.
You send an email message to another person whose email address also ends with Yes, and this message could be blocked as relay mail.
You're attempting to use your home ISP's SMTP (outgoing) server while not connected to the ISP network.The SMTP server can't validate you as an authorized subscriber of the ISP.In addition, you're asking that SMTP server to take your message and then connect to another SMTP server for delivery to the recipient's mailbox.For the first two restrictions — require SMTP authentication or require that you connect to the ISP POP3 (incoming) mail server first — you can make the changes in Outlook in Account Settings.For procedures, go to Change email account settings.