Facebook está com alguns IPs em blacklists, impedindo que usuários recebam emails de notificações, confirmação de conta, etc.
<notification+kjdkkmwh5wmm@facebookmail.com> rejected RCPT
JunkMail rejected – outcampmail003.ash2.facebook.com (mx-out.facebook.com) [66.220.155.162]:22003 is in an RBL, see Blocked – see http://www.spamcop.net/bl.shtml?66.220.155.162
http://mxtoolbox.com/SuperTool.aspx?action=blacklist:66.220.144.162
http://mxtoolbox.com/SuperTool.aspx?action=blacklist:66.220.144.163
http://mxtoolbox.com/SuperTool.aspx?action=blacklist:66.220.144.164