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

Hello folks,

I wanted to pop in here and update the correct answer as the rules and guidelines on automated SMS traffic have changed.

  • Per Cellular Telecommunications and Internet Association (CTIA) Industry guidelines, Intercarrier guidelines and T-Mobile's own Terms and Conditions of Service, automated commercial SMS traffic routing on any network should use short codes.
  • Repetitive mass texts over 10-digit texting are forbidden by CTIA carriers, including T-Mobile. Continued SMS abuse can result in subscriber number being permanently blocked not only by T-Mobile, but also by other carriers, which is outside of T-Mobile control.
  • Commercial trafficking is only allowed through short code, and not through long code (10-digit numbers) and a customer must opt in to receive content.
  • Third-party services can send bulk messages, but such vendors are unaffiliated with T-Mobile.

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238 replies

We have this problem too. Can you help us as well SRickar? Please. I just sent a request to follow you. Thanks.

@srickar we have the same issue with operational SMS emails being blocked as suspected spam.  Can you please follow me so I can PM you details for whitelisting.  Thank you. 

I am also having problems with blocked SMS even though it used to work. Can you please help me out? @srickar

Having the same issue with two of our employees phones. Worked for months now all the sudden they can't get messages. What do we need to do to fix this?

Reason: There was an error while attempting to deliver your message with [Subject: "When the sun rises"] to****** MTA received this response from the destination host IP - ***.222.82.132 - 550 , 550 permanent failure for one or more recipients (****** rejecting banned content)

We just had about 90 t-mobile sms to email gateway addresses rejected.

I work for a large library system and our customers are able to opt-in to receive SMS notifications when they have items ready for pickup that they have reserved or if they have items coming due in 3 days.

We badly need to get our domain whitelisted. Our SPF records are correctly setup. Our library software that handles sending of SMS messages sends through our SMTP relay server that authenticates using our Office 365 account that is the "from address"

@srickar​ can you help us?

BTW, we have a T-mobile business account, we have 80 Alcatel Linkzone hot spots that we check out to our customers at several of our branches. Our BAN# is 964216076.

Userlevel 3
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There was a large spam attack past day or so from spammer using same ESP servers. I had to block them to stop the attack. Please retest.

Userlevel 3
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There was a large spam attack that required aggressive blocking that would have caused false positive blocking. Please retest.

@srickar - our companies web application sms messaging to is getting rejected, follow request sent, we are requesting whitelisting of our companies domain.  Thank you for your help in this matter.

Userlevel 3
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Please retest. There's been a large spam attack that has caused some false positive blocking. I made some earlier adjustments, please retest.

OK, works now, thanks.

Thanks. We'll monitor to see if future notifications to t-mobile customers bounce. Unfortunately, there's no method to re-send the earlier notifications that bounced.

thank you for looking into this.

@srickar​ - our messages are still being blocked, we have proper SPF and DKIM records set.  Is it possible to whitelist our domain?

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I can reinject messages that were blocked, but unfortunately that tends to cause confusion and reaction to outdated alarms, etc. I apologize for the temporary false positive blocking while trying to reign in the spam situation. Thanks.

We noticed about a month ago we were getting blocked.  I work for the public defenders office and we send court reminders to clients.  Unfortunately we do send a lot out so I could see were our domain could be blocked.  How do I get out domain white listed?

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Send me a follow on here with a message and I can search for the block reason. If its public domain, just give me the @domain (full email address is NOT required)., and I can quickly find out why.

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If you have a business account -  you should be able to get personal service from the that dept.   both by phone and email. 

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Hi Mike,

Good suggestions. Yes, all recipient lines would have be part of the primary account holder in order to be eligible for our private email domain service. In this instance, there was a spam attack on April 3rd that required a temporary block of certain traffic that had some false positive blocking. Both scenarios have already been addressed and thanks for looking out.

Hello -

We have a similar issue, from April 19th, I am not getting the text message from my company. Can you please whitelist our domain.

I have also opened a ticket with the T Mobile Tech Support. Ticket No. is   36396061

Thank you

Hi Srickar,

We are experiencing the same issue. From April 15th, my and some of my colleagues using T-Mobile services have stopped receiving SMS from our company domain. I have raised a ticket with the tech support for the same. Ticket no. is  36396061.

May I please request you to follow up and whitelist our company domain. There are two domains. I have provided that on the ticket.

Please help me to resolve the issue ASAP.

Thank you,

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I viewed the ticket and the domain. The domain is failing because of invalid DNS SPF setup. A rejection message is sent back to the mail administrator on every rejection, they should see the rejection reason in the SMTP rejection message. designates x.xx.161.203 as permitted sender. The IP is not authorized to send email on behalf of the domain you are attempting to send email on behalf of. Same issue with the task domain too.

Please see

Sender Policy Framework - Wikipedia

@srickar​ Our company also sends text notifications out to our customers and within the last month we have noticed several blocked messages bounce back. Can you help with this?

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I would definitely be glad to help you. Please send me a follow request for inbox messaging and I can assist in greater detail.

Is this for library overdue notifications? If its a public domain, just tell me the domain and I can do a generic search and quickly see if its blocking.

Yes, it is for overdue notifications. I sent you a follow request.

Hi @ @srickar​I am having an issue getting alerts from Cisco Meraki. Emails from are being blocked to my tmobile number. I will follow you so that you can message me.

Thanks for your help!