Help with 554 authentication error, must login on Microsoft 2007

[mamaschwy]

I am receiving email on Outlook but not able to send. I have used Outlook for a long time with no trouble. I was writing a lot of email on the day
this started. I must need to reset something, but don't know what.

The error code is 554 authentication failed, must login.

I called my server company and can pick up and send email from their site, so the problem must be with Outlook.
B

 

[Silverhazesurfer]

Verify that you have the proper credentials in Outlook's account settings. If you can log into the web interface, there shouldn't be an issue with Outlook as long as the credentials didn't change.

http://support.microsoft.com/kb/287532

If that still does not work, verify that you have ALL of the settings for your provider. Some providers do not use the standard ports for security and etc.