To be more exact, some Facebook mail servers are listed in the Composite Blocking List (CBL), including but probably not limited to these:
- outmail002.ash1.tfbnw.net – 188.8.131.52
- outmail004.ash1.tfbnw.net – 184.108.40.206
- outmail007.ash1.tfbnw.net – 220.127.116.11
- outmail009.ash1.tfbnw.net – 18.104.22.168
- outmail110.ash1.tfbnw.net – 22.214.171.124
CBL is not very informative, but writes:
ATTENTION: If you are running IPSwitch Imail, or similar shared hosting software, please contact the CBL by email. If you are running Ensim, please read this for a workaround. Otherwise, this IP is infected with/emitting spamware/spamtrojan traffic and needs to be fixed.
This will prevent me and others using sbl-xbl.spamhaus.org from receiving some Facebook e-mails. Good thing they are not so important! 🙂
Update This was corrected around midnight (UTC) between Saturday and Sunday.