Email sent to SBCGlobal accounts delayed, all others ISP's accepting properly

In an Windows 2008 r2 domain with Exchange 2007, all email to clients from SBCGlobal.com are being delayed.

Here is the message being received by most employees:
 
Delivery is delayed to these recipients or distribution lists:
 
xx@sbcglobal.net
 
xx2@sbcglobal.net
 
xx (xx3@sbcglobal.net)
 
Subject: Invoices
 
This message has not yet been delivered. Microsoft Exchange will continue to try delivering the message on your behalf.
 
Delivery of this message will be attempted until 11/12/2015 11:54:32 AM (GMT-06:00) Central Time (US & Canada). Microsoft Exchange will notify you if the message can't be delivered by that time.

No error messages are received. The Exchange queue is backed up for SBCGlobal only, no problem with any other domain

Has anyone else begun receiving this delay?
LVL 25
Tony GiangrecoAsked:
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Mark BillExchange, AD, SQL, VMware, HPE, 3PAR, FUD, Anti MS Tekhnet, Pro EE, #1Commented:
Its a DNS issue not not an issue with SBCglobal.net wherever you are sending mail from(where your mail server sends the mail) is not able to do DNS efficently for the domai nname your having issues with or your using active directory for mail dns which imo you should not be this is a bad setup. Either way its a DNS issue.
Mark BillExchange, AD, SQL, VMware, HPE, 3PAR, FUD, Anti MS Tekhnet, Pro EE, #1Commented:
Mainly for inbound mail but it will definetly help with viruses spamming and you will not have DNS issues such as this ever, but we should be using a company like Mimecast to send and receive our email. They will filter out all the junk, alert you to someone hacking you if they are spamming lots of things. There are lots of other companies who provide this service.

If you look at your send connector where is it sending mail from?
Dave BaldwinFixer of ProblemsCommented:
SBCGlobal email is actually operated by Yahoo and has been for years.  Yahoo email is occasionally impossible to get thru to.  They have strange rules.  Sometimes I can get to my Yahoo account and sometimes they block an email address I have been using for years.
Tony GiangrecoAuthor Commented:
The domain was actually greylisted by SBCGlobal. No DNR's were received so we had no definative message to determine what caused the issue. After contacting ATT, they removed the greylisting and mail flowed immediately.

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Tony GiangrecoAuthor Commented:
I found a solution myself.
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