I choose SMTP, but get mail() error

[eluser]nunomira[/eluser]
In my tests I have also got a lot of errors, depending on the server and on what was missing.

Here are some errors for future reference:

451 See http://pobox.com/~djb/docs/smtplf.html.
The following SMTP error was encountered: 451 See http://pobox.com/~djb/docs/smtplf.html.
Unable to send email using PHP SMTP. Your server might not be configured to send mail using this method.

Severity: Warning
Message: mail() [function.mail]: SMTP server response: 502 negative vibes
Filename: libraries/Email.php
Line Number: 1553

Unable to send email using PHP mail(). Your server might not be configured to send mail using this method.

Severity: Warning
Message: mail() [function.mail]: SMTP server response: 503 This mail server requires authentication when attempting to send to a non-local e-mail address. Please check your mail client settings or contact your administrator to verify that the domain or address is defined for this server.
Filename: libraries/Email.php
Line Number: 1553

Fatal error: Maximum execution time of ...

I was astonished to find out that two different servers (unix and windows) didn't allow me to send email because

Code:

$config['newline'] = "\r\n";

was missing from the configuration file email.php.