Error 500: Incorrect authentication data when sending e-mail

[nsns]

Hello.
I have setup a personal e-mail account.
The test connection and send test e-mail works ok.
The incoming mails also works ok
But when i try to send a e-mail i get the error
Error 500: Incorrect authentication data,
How can i resolve this?
Kind regards.

[emillod]

What kind of mail server you're using? Gmail? Something else?