FYI: Updated php 5.2.14 (from 5.2.13) on LAN/development server last night which runs a few cron backups w/mail confirmation overnight. This morning noticed messages not delivered. Checked mail server logs and "p_s: something to block! (Disallowed characters found in MIME headers)" in qmail-queue.log. Examined the quarantined message, it has extra header: "X-PHP-Originating-Script: 10001:script.php^M" inserted before php custom headers.
Bug fix #50907 X-PHP-Originating-Script adding two new lines in *NIX not resolved by this release?
Never had the problem before update... fixed it by editing php.ini and commenting out
;mail.add_x_header = On
BTW: there was no prompt about php.ini.rpmnew during yum upgrade. Will check on production server after php upgrade to see if it is added and make alteration before restarting Apache.
Hope it may be of help to others...