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BCL-4181 asked Paeon commented

Failed to send TEXT messages via Email after Migration

So just today we are seeing where text messages are not being sent through the 2019EX server.
Between yesterday and today I disabled several recieve connectors.

However they appear to be configured the same.

Error messages include:
"451 4.2.0 <user@domain.com> server temporarily unavailable AUP#SNDR(at END OF DATA)"
"421 temporary failure for one or more recipients (phone numbers) server temporarily unavailable AUP#SNDR)"
450 4.4.318 Connection was closed abruptly (SuspiciousRemoteServerError)

I am unsure how to proceed in resolving.
Open to any suggestions.

I looked at Certificates, I looked at receive connectors...all appears fine to me. <-- This was done through the EAC.
Is there something I should be reviewing via the management shell?

Thanks again.





office-exchange-server-administration
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Hi,
Have you configured Text Messaging Delivery on Exchange 2019 server? Make sure Delivery agents and Delivery Agent connectors are not disabled.
Is there any firewall installed? Check if it blocked the message.


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Yes, both Delivery connectors and agents are enabled.

I must have missed a setting between the 2013EX server and the 2019EX server...

Any other ideas? (Any chance it has something to do with my certs??)

Thanks, B

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BCL-4181 avatar image
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BCL-4181 answered Paeon commented

Ok, so after way too much time...the answer was at a Verizon's vendor.
Basically Verizon implemented a new security control, that control went through a 3rd party vendor.
It was only Verizon text messages that were failing and once I contacted the vendor, they reversed something and now all is well.

Thanks for the help.B

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Can you provide any details regarding this 3rd-party vendor whom you contacted to resolve this issue? I'm dealing with the same problem, but when I tell Verizon support that someone else resolved the same issue by contacting a 3rd-party vendor for Verizon's new security control, they would only submit a ticket for me, and rather than identifying this 3rd-party vendor for me, the ticket has now been closed because they "found no network or device related issues." Any help would be appreciated. Thanks.

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AndyDavid avatar image
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AndyDavid answered BCL-4181 commented

How new is the sending IP of the 2019 server?
Seems like the recipients server is greylisting it and backing off the connection
Is it on a blocklist?
https://mxtoolbox.com/blacklists.aspx

"421 temporary failure for one or more recipients (phone numbers) server temporarily unavailable AUP#SNDR)"
450 4.4.318 Connection was closed abruptly (SuspiciousRemoteServerError)

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Nothing is grey or black listed...
Someone suggested updating the SPF record...
Not sure where that might be...

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AndyDavid avatar image
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AndyDavid answered

Check your external DNS:
You can see which servers are listed now for your domain

https://mxtoolbox.com/spf.aspx

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