Outlook is returning Remote Server returned '421 4.3.2 Service not available' for two of my groups.outlook.com groups

I just sent a group message and received the following. I have no idea what these email addresses are or to whom they belong. They are certainly not part of my group.

Delivery has failed to these recipients or groups:

*** Email address is removed for privacy ***
Your message couldn't be delivered. The Domain Name System (DNS) reported that the recipient's domain does not exist.

[snip]

*** Email address is removed for privacy ***
Your message couldn't be delivered. The Domain Name System (DNS) reported that the recipient's domain does not exist.

[snip]

*** Email address is removed for privacy ***
Your message couldn't be delivered. The Domain Name System (DNS) reported that the recipient's domain does not exist.

[snip]

Diagnostic information for administrators:

Generating server: AM9P189MB1699.EURP189.PROD.OUTLOOK.COM

*** Email address is removed for privacy ***
Remote Server returned '550 5.4.310 DNS domain mts.outlook.com does not exist

*** Email address is removed for privacy ***
Remote Server returned '550 5.4.310 DNS domain mts.outlook.com does not exist

*** Email address is removed for privacy ***
Remote Server returned '550 5.4.310 DNS domain mts.outlook.com does not exist

1. Forum software removed those email address. Post just the addresses, not the rest of the error message with a space before the @.

Username @outlook.com will come through. Without the space it won't.

2. Did others in the group to whom you sent this, those with legitimate addresses, receive it?

Don

I just sent a group message and received the following. I have no idea what these email addresses are or to whom they belong. They are certainly not part of my group.

Delivery has failed to these recipients or groups:

******@mts.outlook.com
Your message couldn't be delivered. The Domain Name System (DNS) reported that the recipient's domain does not exist.

Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that their domain isn't properly registered at their domain registrar. Give them the error details shown below. It's likely that the recipient's email admin is the only one who can fix this problem.

For more information and tips to fix this issue see this article: https://go.microsoft.com/fwlink/?LinkId=389361.

******@mts.outlook.com
Your message couldn't be delivered. The Domain Name System (DNS) reported that the recipient's domain does not exist.

Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that their domain isn't properly registered at their domain registrar. Give them the error details shown below. It's likely that the recipient's email admin is the only one who can fix this problem.

For more information and tips to fix this issue see this article: https://go.microsoft.com/fwlink/?LinkId=389361.

******@mts.outlook.com
Your message couldn't be delivered. The Domain Name System (DNS) reported that the recipient's domain does not exist.

Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that their domain isn't properly registered at their domain registrar. Give them the error details shown below. It's likely that the recipient's email admin is the only one who can fix this problem.

For more information and tips to fix this issue see this article: https://go.microsoft.com/fwlink/?LinkId=389361.

Diagnostic information for administrators:

Generating server: AM9P189MB1699.EURP189.PROD.OUTLOOK.COM

******@mts.outlook.com
Remote Server returned '550 5.4.310 DNS domain mts.outlook.com does not exist [Message=InfoDomainNonexistent] [LastAttemptedServerName=mts.outlook.com] [VE1EUR02FT085.eop-EUR02.prod.protection.outlook.com]'

******@mts.outlook.com
Remote Server returned '550 5.4.310 DNS domain mts.outlook.com does not exist [Message=InfoDomainNonexistent] [LastAttemptedServerName=mts.outlook.com] [VE1EUR02FT085.eop-EUR02.prod.protection.outlook.com]'

******@mts.outlook.com
Remote Server returned '550 5.4.310 DNS domain mts.outlook.com does not exist [Message=InfoDomainNonexistent] [LastAttemptedServerName=mts.outlook.com] [VE1EUR02FT085.eop-EUR02.prod.protection.outlook.com]'

Original message headers:

ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none;
 b=ObswAeuInVPPArxXZKxx8fOXlx8k/r8qPLvqOBcIG004uCGENaRozDs7o09QZQxOe+a1E5vmdpm4j0WPmJqizWAbN92WYuJm4ud4GyG3t2+ddqL4VV3z+p5RTb41YLu0YMWTBUQLbIFYtjTI0XKE+OWyB3mYxOecYFMlEeAJPqDWnvUsRtB5zbaC3zDERXp7ACO93DYPMtzDwi+LKnAODcjcCv3ekYfKojRIdNyyjkQ47ZpFu65NeVBxx3LQbSSeClhadmwWo8tjf09K2rZWzI14TF8kBGQXTKhk6leWpj3tRyYcLfCVcK2a93tyOp1PfgFaDEPoeDITlPVY7Ql+Pg==
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=mSJXmNEm7e5YBjc6e7T6w6ZcBaaPg10ioG+gpxTgrSU=;
 b=ONQ+ZIoMTqYNsNAQE9Bmt7/K+OfryOg9cKYW/vEraftDjX00jYeeiX/cOQPTVFdPWBfuVH1CyPRlyYF4zf5iFzF42uG+znBIYqd6hTfRYHCEw+SPCmwoo++bUZz41cCam5WvNWupStZPCkSIgobQvqwYJqPm/Jt4jSh4JCtpplpFcCJ/6OHaiAb0XAuapocXVpH6Z+OLJ5wMWWGshcOkxM2UJD6N2xGduz1WVWJDqsWY6q4GBzNMblL7vPeBb/ZFIzpz8AG0CXMoUttcs3PmMCPGYlVlWITaLCy7kl2JwmLsbO9+o2c0gz4uTrwXLfJ58Ybp9sD+Bvdwn74WIkps+Q==
ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=none; dmarc=none;
 dkim=none; arc=none
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=hotmail.com;
 s=selector1;
 h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
 bh=mSJXmNEm7e5YBjc6e7T6w6ZcBaaPg10ioG+gpxTgrSU=;
 b=A4L9xV5VRmahb6vsapohmqhev8RCK8OkeCMGmLN6gzcIFu23YED9xdXo9M3Rvq3eLds47iwddTqJrmt4Mz0Ysm+1c3fb6Nwrh9s6UqDDH5T0PwSnj1aUdOH8fdG/1jU1RsdAnregDPd71mq0xXYw3l5cSYt4DxXcfFF0d//4gA1dLu5Of4f3Qf5Q7wH+f9ZvaFP2bfFnkcCPqN+8zoJKvHQZQ1xF2gnFtVo7wCzHvUXbRSz4tw4LyytcNBVWVZ1RLYdwh0IE18Dp/6HpHAaOGVy0U/mrWY/WBzd4g+eiwIJp1Viz4thojyux4G6jmxMhABe2YUk9XYwPfgWENrG/sA==
Received: from DU0P189MB1916.EURP189.PROD.OUTLOOK.COM (2603:10a6:10:34c::9) by
 AM9P189MB1699.EURP189.PROD.OUTLOOK.COM (2603:10a6:20b:30d::7) with Microsoft
 SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id
 15.20.5482.6; Thu, 28 Jul 2022 20:49:41 +0000
Received: from DU0P189MB1916.EURP189.PROD.OUTLOOK.COM
 ([fe80::a5cf:3364:7e24:c210]) by DU0P189MB1916.EURP189.PROD.OUTLOOK.COM
 ([fe80::a5cf:3364:7e24:c210%4]) with mapi id 15.20.5458.025; Thu, 28 Jul 2022

* * * Mod note: See the post by Diane Poremsky MVP * * *

Yesterday and today outlook.com is refusing all group email.
I have two different groups that I use weekly. Today I get this message.'

The recipient's email system isn't accepting messages now. Please try resending your message later or contact the recipient directly.

Generating server: BN6PR19MB0962.namprd19.prod.outlook.com
[snip]

---

Sue Hawkins1 wrote:

I don’t know what’s going on.

There aren't many new posts coming in about this problem. Microsoft seems to have resolved the issue for most users.

Are you having this exact problem?

(From the original post)

Yesterday and today outlook.com is refusing all group email.
I have two different groups that I use weekly. Today I get this message.'

The recipient's email system isn't accepting messages now. Please try resending your message later or contact the recipient directly.

Don

* * * Mod note: See the post by Diane Poremsky MVP * * *

Yesterday and today outlook.com is refusing all group email.
I have two different groups that I use weekly. Today I get this message.'

The recipient's email system isn't accepting messages now. Please try resending your message later or contact the recipient directly.

Generating server: BN6PR19MB0962.namprd19.prod.outlook.com
Total retry attempts: 4

*** Email address is removed for privacy ***
Remote Server returned '421 4.3.2 Service not available'

Original message headers:

Received: from SA0PR19MB4412.namprd19.prod.outlook.com (2603:10b6:806:ba::17)
by BN6PR19MB0962.namprd19.prod.outlook.com (2603:10b6:404:74::9) with
Microsoft SMTP Server (version=TLS1_2,
cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.5373.18; Sun, 26 Jun
2022 19:00:06 +0000
Received: from DM4PR19MB6342.namprd19.prod.outlook.com (2603:10b6:8:a7::11) by
SA0PR19MB4412.namprd19.prod.outlook.com (2603:10b6:806:ba::17) with Microsoft
SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id
15.20.5373.18; Sun, 26 Jun 2022 18:59:37 +0000
Received: from DM4PR19MB6342.namprd19.prod.outlook.com

WHAT IS GOING ON WITH OUTLOOK GROUPS??

I create a NEW group to test and it ALSO returns the same error.

* Pinned until August 1, 2022.

I don’t know what’s going on.

Actually, today my group email went through and delivered the email.

Marina Bermoy