[virtual mail hosting guide] can't send mail from other host

[chris_nl]

Hi, I followed the Virtual Mail Hosting guide using postfix/courier-imap etc. Almost everything works: pop3, imap, pop3 secure, imap secure, I can read and send mails using squirrelmail, but the only thing that doesn't work is sending mail.
I've added my host as smtp-server in thunderbird, but when I'm trying to send a mail I can't login, and this is what's in my /var/log/mail/current :

[chris_nl]

I've solved it:

You have to add the following line to your main.cf: