The way the from adress is composed by the mail helper is not valid for all mailserver.
I got the following error:
Warning: mail() [function.mail]: SMTP server response: 501 syntax: Recipient cannot contain a space (<Forgot Password <info@concrete5.org>) in C:\xampp\htdocs\public\concrete\helpers\mail.php on line 122
Fixed it by editing the password_forgot file, line 4
from:
$from = array('info@concrete5.org', 'Forgot Password');
to:
$from = array('info@concrete5.org');
This made the error go away, but obviously delivers a mail without sender name, only email.
to add to that, i just had to put it back to original in order to reproduce the problem.
No i can adjust it again, because my password has been reset before the mail was sent. So cannot login now :).