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

[Alex Carver]

I use the SMS gateway all the time for my alarm system at home
(monitored by a Linux machine at home and sending through my personal
mail server) and there are no delays.  I can trip an alarm and receive
the text message within three seconds using the txt.att.net bridge.

The from address on those messages is whatever I set in the headers.
For example, I have one of my Axis cameras sending a message when it
detects motion.  It sends by way of my personal server and the message
comes out as coming from "cam at acarver.net".  There's a couple scripts
running on another machine watching smoke detectors and those relay out
through my mail server too.  My relay MTA is exim on the server.

The current setup has anything that needs to send an alarm send a
message to a special alias on my mail server.  That gets sent to my
regular user account where procmail picks up the message, duplicates it
and ships it off to the SMS gateway.  The response is immediate and the
text message arrives at my phone the moment it leaves my server.

One thing I used to have in place was a MIME decoder because the message
would be a mess of MIME and text.  I'm not using that currently, though.

On 2015-06-29 12:44, 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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