Who I have the same questioned this topic

On or about 6/23/2021 I stopped getting email-to-text from my company's SMTP server to my <number>@vtext.com address.

When I try to send a test message from my personal GMAIL account, the message arrives in about 10 minutes, which is a long time for an email message to arrive.

Here's the email message we get in our SMTP queued directory.  I have redacted some information

Received: from XXX ([10.1.1.35]) by YYY with Microsoft SMTPSVC(7.5.7600.16601);
Wed, 30 Jun 2021 11:41:38 -0400
MIME-Version: 1.0
From: "Alerts" <Alerts@EMAILADDRESS>
To: [email address removed per the Verizon Terms of Service], [email address removed per the Verizon Terms of Service]
Date: 30 Jun 2021 11:41:38 -0400
Subject: Alert Error -  Download Job Failure
Return-Path: Alerts@EMAILADDRESS
Message-ID: <[email address removed per the Verizon Terms of Service].local>
X-OriginalArrivalTime: 30 Jun 2021 15:41:38.0463 (UTC) FILETIME=[6A45CAF0:01D76DC6]

Here is a file that is found in the BadMail folder on our SMTP Server

From: postmaster@DOMAIN
To: Alerts@EMAILADDRESS
Date: Tue, 29 Jun 2021 07:27:26 -0400
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary="9B095B5ADSN=_01D6578A2B743B83000000BCHADES.mont.local"
X-DSNContext: 7ce717b1 - 1386 - 00000002 - C00402D1
Message-ID: <xC9AZvoMk00000016@DOMAIN>
Subject: Delivery Status Notification (Failure)

This is a MIME-formatted message.
Portions of this message may be unreadable without a MIME-capable mail program.

--9B095B5ADSN=_01D6578A2B743B83000000BCHADES.mont.local
Content-Type: text/plain; charset=unicode-1-1-utf-7

This is an automatically generated Delivery Status Notification.

Unable to deliver message to the following recipients, due to being unable to connect successfully to the destination mail server.

[email address removed per the Verizon Terms of Service]
[email address removed per the Verizon Terms of Service]

--9B095B5ADSN=_01D6578A2B743B83000000BCHADES.mont.local
Content-Type: message/delivery-status

Reporting-MTA: dns;DOMAIN
Received-From-MTA: dns;SENDER_SERVER
Arrival-Date: Sun, 27 Jun 2021 05:35:01 -0400

Final-Recipient: rfc822;[email address removed per the Verizon Terms of Service]
Action: failed
Status: 4.4.7

Final-Recipient: rfc822;[email address removed per the Verizon Terms of Service]
Action: failed
Status: 4.4.7

--9B095B5ADSN=_01D6578A2B743B83000000BCHADES.mont.local
Content-Type: message/rfc822

Received: from SERVER([10.1.1.35]) by DOMAIN with Microsoft SMTPSVC(7.5.7600.16601);
Sun, 27 Jun 2021 05:35:01 -0400
MIME-Version: 1.0
From: "Alerts" <Alerts@EMAIL>
To: [email address removed per the Verizon Terms of Service], [email address removed per the Verizon Terms of Service]
Date: 27 Jun 2021 05:35:01 -0400
Subject: Found 2 Off-Hours Error Alerts for 2021-06-27
Return-Path: Alerts@EMAILADDRESS
Message-ID: <[email address removed per the Verizon Terms of Service].local>
X-OriginalArrivalTime: 27 Jun 2021 09:35:01.0651 (UTC) FILETIME=[B3E96630:01D76B37]

As I said, this started on 6/23 approximately.  Previous to that it was working correctly and we would get our alert emails when something needed to be addressed in the system.  Now, we do not get those emails and we have lost visibility on possible critical issues.

Is there some SPF or configuraiton change that I need to make on the STMP server?  I'm not entirely up to speed on the administration of the server.