In Drupal 5.1 When a user requests a new password, if this error occurs:
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warning: mail() [ function.mail ]: mail() - newline subject header, possible injection, mail dropped in yoursite info here/includes/common.inc on line 1972.
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then in file includes/unicode.inc remove the \n at the end of line 252
$output .= ' =?UTF-8?B?'. base64_encode($chunk) ."?=\n";
This solution was found by a sharp eyed, programming genius friend. The explanation was that the \n is the add new line command which is not needed in the subject line of an email. Thus, it seems it is something to change in the next version of Drupal.
Interestingly, the problem did not occur after a fresh installation, but did occur when importing a copy of an installation.
