We have multiple users in our IT department within my company who receive system generated SMS texts on their Verizon business phones created from our Linux server based email using the <phonenumber>@vtext.com that is not working as of early July. I've seen all the posts from people who are getting spammed from vtext.com and I understand action needs to be taken to address that but what is being done for the rest of us who rely on legitimate use of vtext.com? It appears to be working (most of the time) from manually created email from gmail and Outlook 365 mail clients/servers but not from private internal servers (?)
My email admin says this is the error he is seeing:
(DCID 22713639) Message 1545754868 to ##########@vtext.com delayed. Reason: 4.3.1 - Mail system full ('452', ['4.1.0 <[email address removed per the Verizon Terms of Service]> server temporarily unavailable AUP#MXRT']) 
Mail system full - what does that mean?
Server temporarily unavailable - what does that mean?
I called Verizon support 4 hours ago and was told she recognized this as a problem and would call me back (no call back).
Forgot to mention, after about 3 days, I receive an email saying the email I sent is undeliverable with delivery expired, message too old
The following message to <##########@vtext.com> was undeliverable.
The reason for the problem:
5.4.7 - Delivery expired (message too old) [Default] 452-'4.1.0 <[email address removed per the Verizon Terms of Service]> server temporarily unavailable AUP#MXRT'
justworking, we are grateful for the details you provided. We want to do everything we can to help you. We sent you a Private Note. Ple4ase respond at your earliest convenience.
If you search the forums you will see it hasn't been working for most for a long time now. Mary