550 5.7.1 Client does not have permissions to send as this sender
When configuring the receive connector in Exchange 2007, I find out that users using SMTP email client like Outlook Express and Thunderbird can receive email but cannot sent email through Exchange as the SMTP server. They get the following error:
“Protocol: SMTP, Server Response: ‘550 5.7.1 Client does not have permissions to send as this sender’, Port: 25, Secure(SSL): No, Server Error: 550, Error Number: 0x800CCC78”
Tags: Exchange server, Mail server