Any mail function within MediaWiki (mail a new password, email user, confirm
email, ENotif) is potentially(*) broken in a certain php version  due to a
missing space. This has been reported by a user.
Fix by adding an additional space after the "-f" option letter.
Example 3 in , which was used when implementing this in UserMailer.php, does
not show the space, but it helped to get a touchy php mail() implementation running.
Therefore I suggest to change line 132 in UserMailer.php from
mail( wfQuotedPrintable_name_and_emailaddr($to), $subject, $body, $headers,
mail( wfQuotedPrintable_name_and_emailaddr($to), $subject, $body, $headers, "-f
 PHP: 4.3.10 (apache)