Today i come across an error while sending email from outlook 2007.While sending email i got an error message that "Error 550: Server must be authenticated".This can be rectified as follows
Click on "Tools" menu in the Microsoft Outlook.Then choose "Account settings", Double click on the email which you have problem. A new window pops up.At the lower right corner of the window there will be a button labeled "More settings" Click it. Go to the "Outgoing server" tab and put a check in the box labled "My outgoing server (SMTP) requires authentication" under that you will see 2 buttons, Select the button labled "Use same settings as my incoming mail server", Click "OK" then click "Next" at the next menu, then click "Finish" at the next menu and finally "Ok" at the last menu. Restart Outlook and you should be fine.
Email Error : "Server responded 550 must be authenticated" : Solved
by Shabeer ibm