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New Member

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3 Messages

Tuesday, July 20th, 2021 6:45 PM

Error 550 5.1.1 when using Email to SMS Gateway

I am trying to send mass texts out to a large group of people and have created a spreadsheet with all their carriers and corresponding SMS gateway addresses. What is so odd is that many of my AT&T recipients have been able to receive the messages, except for one. We looked at the settings on her phone and nothing appears to be amiss. Her daughter's phone (under the same plan within AT&T) had no trouble receiving the message using [10 digit phone number]@txt.att.net. 

I cannot figure out why the one recipient kicks back an error message that the address doesn't exist. I have checked the number multiple times. I have also tried from different sender servers--both Outlook and Gmail...same error message for the recipient's SMS gateway address.

ACE - Expert

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35.6K Messages

3 years ago

Perhaps she has had e-mail to text blocked on that number (and has forgotten).

New Member

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3 Messages

3 years ago

She receives texts from other groups (like the local public school system and appointment reminders), but they may not be SMS gateway. How does one block or un-block email to text on a single number? This is not something that would have been done intentionally.

ACE - Expert

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35.6K Messages

3 years ago

My understanding is that you can block all uses of the SMTP->SMS gateway for your number.  Not one particular sender; all senders using the e-mail gateway.

Vendors that use a different mechanism (e.g. Twilio) wouldn't be blocked by that.

New Member

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3 Messages

3 years ago

This particular user did not knowingly block the SMS gateway addresses.

Is there a way to check this and reverse the block?

ACE - Expert

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35.6K Messages

3 years ago

My understanding is that it can be done by Support.  I assume it could be checked on, and possibly undone, by support.

New Member

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3 Messages

3 months ago

3/2024: Email >>to>> @txt.att.net   ::Same Issues Wasted 4 hours on Customer Support  Chats/ Social media>>Went to Store>> They advised to Call 611 ask for "Advance Support".

My Account showed that this feature was turned off / uncheck for both txt and mms...Took them 45 minute to locate..

It would be nice if the ATT Article : https://www.att.com/support/article/wireless/KM1061254

Would be amended to include Troubleshooting effort for SMTP Delivery 550 Errors to call 611 "Advance Support"

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