NOTE: Thanks to Ben Totanes for pointing out that this now applies to all AT&T (att.net) accounts and sbcglobal.net accounts.
I've thought about this a great deal, and I think my initial concerns have proven true. Taking two companies who were neck and neck in the race for nations worst tech support and merging them was a very bad idea. This became even more apparent as I was troubleshooting an issue where one of our clients was unable to send email to a specific domain (AT&T's Bellsouth.net domain).
One of our clients recently noticed their messages to BellSouth.net were being delayed and then they received an NDR. The error messages they received looked like: "This is an automatically generated Delivery Status Notification. Unable to deliver message to the following recipients, due to being unable to connect successfully to the destination mail server."
There are a few steps you can take to greatly expedite the troubleshooting process:
1) Check a site like http://www.mxtoolbox.com/blacklists.aspx to make sure you are not on a blacklist.
2) Perform an NSLookup for Bellsouth.net on your mail server.
H:\>nslookup
Default Server: appserver.local.dcaglobal.com
Address: 10.100.111.2 > set type=mx
> bellsouth.net
Server: appserver.local.dcaglobal.com
Address: 10.100.111.2
Non-authoritative answer:
bellsouth.net MX preference = 10, mail exchanger = gateway-f2.isp.att.net
bellsouth.net MX preference = 10, mail exchanger = gateway-f1.isp.att.net gateway-f2.isp.att.net internet address = 207.115.11.16
gateway-f1.isp.att.net internet address = 204.127.217.16
3) From command prompt attempt a telnet connection to a Bellsouth mail server on port 25 (e.g. telnet 204.127.217.16 25). Pay attention to the response, if your connection is rejected you are most likely on one of their blacklists.
Good response: 220 isp.att.net - Maillennium ESMTP/MULTIBOX frfwmxc11 #116
Bad Response: 550-65.182.55.3 blocked by ldap:ou=rblmx,dc=bellsouth,dc=net
550 See http://www.att.net/bls_rbl/ for information.
4) If you are blocked, send an email to bellsouth_unblock@abuse-att.net including
a. Originating email domain:
b. IP Address of mail server
c. Company name:
d. Phone Number:
e. Contact Email:
f. Time issue was first noticed:
g. Error received:
h. Message Header (if you have it):
5) You can also request they unblock your email address here: http://worldnet.att.net/general-info/bls_info/block_admin.html
This issue took far more time to troublshoot than it should have due to the obscure/misleading NDR message from Bellsouth. I'm hoping that by posting this I might save a few people a bit of time.








