[ale] Email to txt.att.net (AT&T Mobile - SMS) being delayed

[Stephen R. Blevins]

Do you get the same behavior if you use phonenumber at mms.att.com ?  I've
been using that successfully for some time, but I have never had to be
concerned with timing issues.

Stephen R. Blevins
stephen.r.blevins at gmail.com

On 06/29/2015 03:44 PM, Lightner, Jeff wrote:
> Note this is not a question about the normal “your SMS messages may be
> delayed or isn’t guaranteed” if you’re not using their SMS for business
> service.   This is a question that appears to be unique to the way AT&T
> is handling our text messages from Linux vs. the way other carriers such
> as Verizon and T-Mobile do.
> 
>  
> 
> 1)       Is there a way to configure Sendmail so that mail it relays to
> other hosts use the short name of the Linux server where it originated?
> 
> 2)      Alternatively, does anyone know if AT&T is delaying email
> because it does a hostname lookup for sender email when going to
> @txt.att.net.   (i.e. Iis there any benefit in making a
> *.<ourdomain>.com DNS record so any of <hostname>.<ourdomain>.com hosts
> resolve an IP to solve the issue at AT&T?
> 
>  
> 
> DETAILS:
> 
> We got a complaint today that email from one of our servers to going to
> AT&T Mobile phone is being delayed when it comes from one of our Linux
> servers but not when it is sent via Outlook/Exchange directly.
> 
>  
> 
> The sending server is using RHEL5.10 and Sendmail.  It relays through a
> MS Exchange server here for all mail.
> 
>  
> 
> The mail is sent to <phonenumber>@txt.att.net when we need to send a
> text from our application.  
> 
>  
> 
> My findings:
> 
> 1)       The mail sent to @txt.att.net per /var/log/maillog is being
> sent as soon as the command is run.
> 
>  
> 
> 2)       The relaying Exchange server is accepting the mail and is
> sending it to txt.att.net almost immediately.
> 
>  
> 
> 3)       Mail going to Verizon (@vtext.com) and T-Mobile (@tmomail.net)
> using same command line on Linux is appearing on the phones almost
> immediately. 
> 
>  
> 
> 4)      Sender in relayed emails is root@<server>.<ourdomain>.com
> <mailto:root@%3cserver%3e.%3courdomain%3e.com>
> 
>  
> 
> 5)      Issue occurs if I do telnet to port 25 of the Exchange server
> from the Linux server.   (i.e. Do direct smtp and bypass Linux Sendmail
> config).
> 
>  
> 
> 6)      Test from Outlook confirms that the email goes to the AT&T phone
> text message almost immediately.
> 
>  
> 
> 7)      We found a Windows server running an application that does smtp
> to the Exchange server on port 25.   When it sends messages to
> @txt.att.net they are received on the phone almost immediately.   That
> message was also sent to a real mailbox and review of headers there show
> it took the sending server’s shortname rather than FQDN.
> 
>  
> 
> 8)      Based on findings from 8 I redid the test from 5 using the
> shortname of the Linux server rather than the FQDN it usually sends
> (which I’d used in test 5) and this also went to the phone almost
> immediately.
> 
>  
> 
>  
> 
> /Jeffrey C. Lightner///
> 
> /Sr. UNIX/Linux Administrator///
> 
>  
> 
> DS Services of America, Inc.
> 
> 2300 Windy Ridge Pkwy
> 
> Suite /600 N/
> 
> Atlanta, GA  30339-8461
> 
>  
> 
> P: /678-486-3516/
> 
> C: /678-772-0018/
> 
> F: /678-460-3603/
> 
> E: /jlightner at dsservices.com/
> 
>  
> 
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