Error 550 authentication is required for relay is usually crops up whenever you try to send emails and unable to send it due to the SMTP server issue. An authentication is required that means you have to enter your ID and password in order to send emails, when SMTP server is unable to deliver your send emails to the sender. This is not so hard process, which can’t be performed by a user. You can also eliminate this error 550 and able to send messages again. For this, if you any help, you can go for Microsoft Live Chat support. Here, you can get on time solution in no time.