Email to SMS ( is blocking our domain for spam.

I work for a local fire department, which uses the gateway to alert members of the fire department with (T-Mobile service) of emergencies/disasters. We use similar gateways from other carriers for those respective members, and they are without issue at this time. This system from T-Mobile has worked flawlessly for the last 2 years, until recently, which we are now getting bounced by the server and getting the mail messages kicked back with the following error (X's represent the member's phone number): gave this error:
permanent failure for one or more recipients (

i've tried sending messages individually, and even sending out messages as MMS, and I'm still getting bounce backs.

I see "srickar" on this site answering questions, as the spam admin for, and I was wondering if they'd be able to point me in the right direction.

Not only am I the one handling this issue... I'm also a T-Mobile user, and am one of the end users effected by it.

Thanks for any input.


Best answer by srickar 29 April 2021, 15:50

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153 replies

Userlevel 6
Badge +15

I saw this issue before for emails with over 55 characters in the email contents and subject line, but this appears to be resolved. You'll want to Community-2153​ and have a Trouble Ticket filed to get this fixed.

I work for a CRM company using email to send SMS alert to our users, and tomomail has started blocking us.  @srickar please help!  I've talked to 8 different people over chat/phone over the last two days trying to get resolution for what sounds like an issue you're very familiar with.  I followed you yesterday, but not sure what to do next.  Your Support team tells me they have discontinued support for altogether so there is nothing they ca do?  HELP!!  My case # is 40179836

@srickar​  please let me know how to  DM you or feel free to reach me on any of the contact info in my ticket.  Thank you!

Userlevel 3
Badge +4

Glad I could resolve your issue. Thanks!

Hello srickar

I am in a similar boat to others in this thread, with alert messages from a single source to the SMS gateway being blocked from reaching T-Mobile and some Sprint users.  Coincidentally, this has been by the Barracuda appliance/service and since 22 January.

How shall I submit further problem description and headers for resolution?

I've been watching the traffic in other threads but not seen much method or hope for a fix until just now.

Hoping you can help.


Userlevel 3
Badge +4

Hi. I cannot message you yet. Can you please send me a follow through inbox?

Apologies.  Still figuring out the protocols here.

(I think) I just sent follow request

Userlevel 3
Badge +4

Thanks. I sent you a D.M.

Hi! I also have the same problem with this. Would you be able to help me out? I will send you a personal message right now. Thank you!

I too am being blocked as spam when I send an email to  This has worked for me for years.  Would someone please post the solution or instructions how to send a dm to get it resolved?  Thank you.

@tmo_mike_c; @srickar@tmobile-admin

Userlevel 3
Badge +4

I sent you a follow request. Please accept and send me a DM please.

@srickar​ - I accepted follow request and sent dm with particulars.

Hi, I have a raspberry PI at home that has been sending out emails/(SMS Messages) to my Tmobile phone for years and all of a sudden about a week or so ago it no longer works.  My PI still sends emails to my other email addresses, just not the phone.  I am sending it using postfix and relaying through my personal domain email account.  Is Tmobile blocking certain domains now?  I can send an email directly from my email client, just not through the relay.  Does Tmobile need to whitelist my home IP address?  I contacted support but they had no idea what I was talking about.  Thanks in advance. 

Userlevel 3
Badge +4

yikes, sorry to hear that. I can help, just respond to my follow request. The typical reasons are keyword match block, sender policy framework, or double relay forwarding.

I am having the same issue - what can I do to get assistance? t mobile is blocking our emails from our domain @srickar​ can you please help me - I even messaged this on another thread. I have had no helps to date.

Userlevel 3
Badge +4

Be glad to help. Sending a DM follow.

@srickar​ I'm having the same problem where emails to are being blocked but it's working for every other carrier.


I also work for a county organization that send email to text from a gmail account and is being blocked. How do I get whitelisted for this to be allowed? The text that is being sent looks like this so I am not sure why its being blocked:

MSG:Alert Id: 471626

Alrt: Flash On Any, St: New, Dev: SIGNAL 197 - Dixie Hwy @ Aviation Wy, Tm: 11/6/2019

(Con't) 2 of 2

12:51:35 PM, Crit: Critical, Evt: Flash Dixie Hwy Aviation Wy N/A

any help would be greatly appreciated!

Userlevel 3
Badge +4

Messages are failing when they fail to include a subject. The subject is not required but highly recommended due to spammers not including subjects in their attacks. If a subject would be included, and include a name tagged with the recipient address, the emails will pass. Webmail providers like gmail, yahoo, aol, etc are highly abused by spamming entities because of the accessibility to use free accounts by the thousands.

1.28 MISSING_SUBJECT_2 META: Missing Subject: header

Well this is an emergency alert system and we cont control the information

from the email. When I get it through an email it shows a subject.

Userlevel 3
Badge +4

The subject field is blank hence the scoring I had previously provided. The dash there is actually just a character to indicate null value.

1.28 MISSING_SUBJECT_2 META: Missing Subject: header

Ok well again, it is a system generated email that we cannot control the

information it provides. Again we have other employees with different

carriers that do not have an issue, and I also have been receiving these

texts for about a year or two now without an issue, so am unsure why now

all of a sudden it is being flagged as spam?

Userlevel 3
Badge +4

Each carrier has their own attacks, thresholds, and anti-spam vendors. Our provider is a large anti-spam corporation. Like I had mentioned previously, webmail based domains like gmail are under higher weighted scrutiny for spam volume because of the simplicity to register millions of email accounts to originate spam from.

In this particular case, the gmail account is sending out an alert that's missing a subject which is a significant field that should be populated. Anti-spam expressions, rules, and volume, and type of attack vary greatly from one moment to the next so messages that previously pass are not guaranteed to pass 5 years later, much less 5 min later due to how attacks evolve that require reactive scoring values. Global anti-spam definitions are loaded every 15 minutes based on spam trends. Unfortunately, spam attacks evolve and so do the filtering required to block them. As example here, you can see spammers register emails, without subjects, and spam all carrier domains trying to entice users. These score values are not intended to punish legitimate users, but to inhibit spamming.

The spammers goal is to get replies to harvest for future mailing list attacks.

This is one example of thousands of throw away email addresses simultaneously sending out spam attacks. Sending messages that contain as minimal as possible fields to measure as possible is the spammer goal, and one of those goals is to strip off subjects.

It would be ideal to include subject. If possible, send alerts from private domains in lieu of freemail clients that are collocated amongst spammer entities. Another potential ability would be to auto-forward gmail messages to a gmail account that auto-populates a subject before forwarding the final recipient address

@srickar - We are having the same problem receiving a 550 permanent error blocking email messages to but working fine with other carriers. Any help will be greatly appreciated. Thank you.

Please let me know what we can do to get this resolved, or if we should

just go to another carrier that doesn't have these issues.


On Thu, Nov 7, 2019 at 3:47 PM Joshua Leuthold <>