Email to text message service is blocking messages

Our gated community's entrance system sends a text message to the resident when their guest arrives at the gate. Per your instructions, the message is emailed to the recipient's 10-digit wireless number, followed by @txt.att.net. We send about 100 messages per day to AT&T customers. The messages are sent from "bentwaterpoa.com" domain. The sender is "[email scrubbed]".  The text messages are rejected with the following message:

att-e2xms-ibgw-5001a.ext.cloudfilter.net rejected your message to the following email addresses:

[email scrubbed]
Your message was rejected by the recipient email server. Please check the recipient's email address and try resending your message, or contact the recipient directly. For more tips to help resolve this issue, see DSN code 5.1.0 in Exchange Online - Office 365. If the problem continues, contact your email admin.

att-e2xms-ibgw-5001a.ext.cloudfilter.net gave this error:
40.107.93.43 blocked AUP#CDRBL

Diagnostic information for administrators:

Generating server: IA1PR17MB6621.namprd17.prod.outlook.com

[email scrubbed]
att-e2xms-ibgw-5001a.ext.cloudfilter.net
Remote server returned '550 5.1.0 40.107.93.43 blocked AUP#CDRBL'

Original message headers:

ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none;b=lzZZOZR51/8qDtwHYz2peI9Jv3LcqqhMrtc1lLgloecIQoDMxtKOQoL4RBxxIxBrjt+4Yu7P46fXC4EoXUAOOWbI+vXfe8pf76Pu5xSzF9eF467bNJVccjMnqEfdUQDTRgv2tIjHECROwkRKhAWfg/RVXfSkt/eo28USryX7IoWDK/ELBXAmbWl8vLmmg7RRO20xz6xbolPVtj17vMUJHsEmSh70e3BlrMRBn8tIt+NSxohxFXKN9kVDVUp6KMllHREUSIuy6wBOaSHH9g1Wn7l0CqErSX0qpxHXkbGHOTwE8m4bwmLbd+vMiORYbX2MBZ/47SZ6PPlvuI6+uqSZQA==ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com;s=arcselector9901;h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1;bh=OKAVf+ZmP+kg7/oH2cfUwmsUKD0rCedz/sW9xyww98s=;b=Sjy/vNcZWx27xOybYuF6n+17fZmHdrr/qdr16po2iJuCEVFPaO8gEN2zKZ2cqbgRcVzlzcxM2GSTUvjIkn4YQGUsm8u2GIm1eUNiLDD+4GP6M/lBNRZ8bD8r1MdESasH1Zsn0lombElo9JL0bsdSxOKYfUICAb0iBNYrwpg3fRcgx+O6nuX13fMdOb7XtOobvJqPIqmdij8gK9UqQqHUZx4ZJgmIGX0lfYJvJaGK+BiEphiwKXJWvl71Af4W7XZwrxBB039SEOkSmOLgnQbQXUxCA8313qqwPgPur9GLL0CY2KGqMU75sYGUzR9cRC6AGnyVClCAzJqi5vZDTv5o1A==ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=passsmtp.mailfrom=bentwaterpoa.com; dmarc=pass action=noneheader.from=bentwaterpoa.com; dkim=pass header.d=bentwaterpoa.com; arc=noneDKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=BWpoa.onmicrosoft.com;s=selector2-BWpoa-onmicrosoft-com;h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;bh=OKAVf+ZmP+kg7/oH2cfUwmsUKD0rCedz/sW9xyww98s=;b=KN1n2VhL1CgBVeZojYtudHA0bkPULtUZGDVMxtEgaL8ZC10Pd3c5VUzNZpHgYgJkJQaFwHeE3bhElA/XGvvy7Tkq74sg2p6D306TZf530bRP8ZcsmtJwI2VGHoojoNHwZI0sCGKXbg/fHJ/hqWO++AzxIvF+dN7qrdW/o3BDaAg=Authentication-Results: dkim=none (message not signed)header.d=none;dmarc=none action=none header.from=bentwaterpoa.com;Received: from MW4PR17MB4732.namprd17.prod.outlook.com (2603:10b6:303:109::14)by IA1PR17MB6621.namprd17.prod.outlook.com (2603:10b6:208:3f6::12) withMicrosoft SMTP Server (version=TLS1_2,cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.6387.35; Wed, 17 May2023 13:45:32 +0000Received: from MW4PR17MB4732.namprd17.prod.outlook.com([fe80::e89b:bb63:99f8:39a]) by MW4PR17MB4732.namprd17.prod.outlook.com([fe80::e89b:bb63:99f8:39a%5]) with mapi id 15.20.6387.032; Wed, 17 May 202313:45:32 +0000