E-mail to SMS being blocked due to suspected SPAM

I work for a trucking company, and we use e-mail to SMS to send out dispatch messages to our drivers for load information. Drivers can then reply to those messages to have conversations with dispatchers who operate via e-mail.

This has been working for years; however, as of 3/26/2018, it seems our entire domain has been blocked by T-Mobile servers. E-mails sent to are rejected with 550 errors. I have tried sending as plain text, e-mail, short, long, with picture, and just about every way I can think of, but it's always blocked. Messages sent to all other mobile carriers are still going through just fine.

I have tried calling support, but no lower-level techs seem to even understand what E-mail to SMS is, and they just exhaustively try things that are specific to one individual phone. They supposedly escalate the issue, but we never hear back. I am desperately searching for someone within T-Mobile who can actually tell me why my domain is suddenly being blocked. This functionality is critical for our drivers to do their jobs; I'd prefer my answer to those drivers not be "sorry, find another carrier" as they keep asking us why their messages are failing while all the non T-Mobile users are moving along just fine.

@srickar​ - I've seen where you've been super helpful to some people; is there any chance you could help us out, too? I can PM you specifics.


Best answer by tmo_chris 5 November 2019, 00:21

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Correct. SPF is a solely owned domain owner controlled configuration.

@srickar​ thank you for the quick response!

typically we only use if for verification codes but yesterday we sent 4800 (8 messages x 600 customers) so i understand what you are saying. Can you unblock so we can continue to verify. I will review the document and see if blasts can go another route.

Thank you

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I have removed the outright block, but please note that exceeding rate control volume is still possible and I cant circumvent since rate control is a global setting. For this type of A2P automation, the traffic should move to a shortcode provider like Syniverse, Twilio, Sybase, etc. These dedicated routes have different anti-spam policies for vetted traffic and perform ENUM lookup automatically to find the right carrier owner.

Since you are using email, if a subscriber ports between different carriers, you are essentially emailing a stale address which ENUM lookups are performed in real-time by the shortcode operator. Also, if a subscriber were to swap numbers and a former number is now assigned to a new user who's getting these email blasts, they could report it to FCC for TCPA violation. Something to consider as to why enterprise compliance is crucial these days. Thanks.


Understood and thank you for unblocking, we're likely going to use Iphone/Android notifications to replace the text blast model.


Good afternoon!

We seem to have found our way on to the T-Mobile blacklist, this is what we are getting:

"recipient-domain": "",

"id": "8y7NCQN5T_iaNTMnARFxIQ",   

"campaigns": [],

"reason": "blacklisted",

"user-variables": {},

"flags": {

"is-routed": false,

"is-authenticated": true,

"is-system-test": false,

"is-test-mode": false

Our service sends emails to text messages for Doctors and it has been working perfectly for about a year to one of our clients who is a T-Mobile user, but last Friday we started getting bounce back emails with that reason code.

Would you be able to remove from your blacklist?

I would very much appreciate it!



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Found the reason. That email address is using "postmaster". It's such a generic email user name that it was blocked for unrelated use by spammers. ";;; etc. Please change the presented configuration so that it's not so generic.

Nice!  Thanks for that, I'll see if we can get that changed by our mail host.

Much appreciated!

I need assistance o one seems to be able to help me when I call in support...  Getting this message

Your message to has been blocked. See technical details below for more information.

I see my emails going through, but not text message. 

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Seesnap is inserting a link. That is not permitted. Otherwise, all other test messages are delivering that do not contain this link.

@srickar​ I'm having this issue too are you able to assist?

<>: host[x.x.x.x] said: 550 permanent

    failure for one or more recipients ( (in

    reply to end of DATA command)

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Yes I sure can help! I sent you a follow request.


We already figured it out with you on another forum.

Thanks again for your help.

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Glad to hear could get it resolved, but was replying to @magenta516558


Hi,  you were able to help me a couple of months ago, but we just started seeing a block again.  Not sure why.  Here are the details of the message:

<>: host[] said: 550 permanent

    failure for one or more recipients ( rejecting

    banned content) (in reply to end of DATA command)

---------- Forwarded message ----------





Date: Fri, 18 Oct 2019 12:25:54 -0500 (CDT)


602-xxx-xxxx replied to Ad Code(RKTxxxx) with: 'Price ?'

This was the first bounce we got, but subsequent messages are bouncing as well.  Can you give me an idea of what could be causing the issue?  We haven't changed anything wrt to content sent.  maybe a rule change?  Any help is appreciated.  I can be reached at 877-848-4045.  Thanks

I'm getting this as well, can anyone help?

I actually have Walmart Family Plan via T-Mobile

SMTP error from remote server for TEXT command, host: ( reason: 550 permanent failure for one or more recipients (

54 rejecting banned content)


Hi, just checking in again on this.  Is there someone at T-mobile I can get in touch with about whitelisting?

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generic reply envelopes such as info@, postmaster@, webmaster@, root@, sales@, are spam sources and are not permitted at this time.

So, you're filtering on the info sender?  Is there a way to get whitelisted?  We're not sending content unless someone asks for it.

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Sorry cannot whitelist external senders. There is a spam outbreak that is using info@ so I cannot unblock at this time.

We are getting a similar issue with our employees/your customers. Is there anything my company can do?

@srickar​, I am having the same problem. WE were successfully sending emails (domain authenticated) yesterday from our field services devices to TMobile numbers. This morning, they seemed to be blocked. What can we do?

From our email provider SendGrid:

Received by   




2019/10/23 10:17am UTC-04:00

The server blocked this message from being delivered. While we won't try to send this message again, we will attempt to send new messages to this address in the future.

You can view all addresses in your Blocks suppression group. Learn more.

Full response from the server:

550 permanent failure for one or more recipients (

@srickar, let me know if you need the sending domain, or the phone numbers that were sent to.

Thank you @srickar for your reply.

We generate appointment confirmations to clients a day before their

appointment.  Our email address is @colorboxsalon. Here is

the response I am getting when emailing to a T-Mobile client:

This message was created automatically by mail delivery software. A

message that you sent could not be delivered to one or more of its

recipients. This is a permanent error. The following address(es) failed: SMTP error from remote mail server after end of

data: host : 550

permanent failure for one or more recipients (

rejecting banned content)

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If possible, please edit/remove identifying information in your cut and paste.

The appointment reminders are passing just messages that discuss Facebook. I checked, and the reason why this is blocking is a facebook URL is pasted in the message body. This type of block is necessary because spammers are sending out similar facebook spam containing adult content. If you could please remove the facebook footer from messages they will also start passing.

Thank you, srickar!  That did the trick.