Google/Microsoft: read error: FAILED_PRECONDITION: read error (104): Connection reset by peer

Does anyone else have trouble getting email delivered to their self-hosted discourse instance but only from large email providers such as Google and Microsoft? I am able to send emails to my instance using a local email server, iCloud, and ProtonMail consistently but with Gmail (including its Workspace email) and Office 365 based emails I get the following error:

Message not delivered

There was a problem delivering your message to xxx@example.com . See the technical details below.
The response was:

read error: FAILED_PRECONDITION: read error (104): Connection reset by peer

Reporting-MTA: dns; googlemail.com
Arrival-Date: Tue, 02 Nov 2021 13:12:55 -0700 (PDT)
X-Original-Message-ID: <CAAY3Td6W+9uYHRVJ6A8=9pG4LhaJrYRAN16CWe=3_2gG9TH7Uw@mail.gmail.com>

Final-Recipient: rfc822; xxx@example.com
Action: failed
Status: 4.4.2
Remote-MTA: dns; reply-mx.example.com. (xxx.yyy.zzz.163, the server for
the domain example.com.)
Diagnostic-Code: smtp; read error: FAILED_PRECONDITION: read error (104): Connection reset by peer
Last-Attempt-Date: Fri, 05 Nov 2021 17:08:12 -0700 (PDT)

From: Kartik <yyy@gmail.com>
Subject: Test from Gmail
Date: Tuesday, November 2, 2021 at 3:12:39 PM CDT
To: xxx@example.com

OR 'Socket error ConnectionReset' with O365:

From: Microsoft Outlook MicrosoftExchange329e71ec88ae4615bbc36ab6ce41109e@example.onmicrosoft.com
Sent: Wednesday, October 13, 2021 10:32 AM
To: xxx@example.com xxx@example.com
Subject: Undeliverable: email subject here

Delivery has failed to these recipients or groups:
xxx@example.com (xxx@example.com)
Your message wasn’t delivered. Despite repeated attempts to deliver your message, a connection to the remote server couldn’t be made.
Contact the recipient by some other means (by phone, for example) and ask them to tell their email admin that it appears that your email system is unable to connecto their email system. 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: Fix email delivery issues for error code 550 4.4.7 in Exchange Online | Microsoft Docs.

Diagnostic information for administrators:
Generating server: example.namprd11.prod.outlook.com
Receiving server: example.namprd11.prod.outlook.com
Total retry attempts: 2
xxx@example.com
10/13/2021 4:32:36 PM - Server at example.namprd11.prod.outlook.com returned ‘550 5.4.317 Message expired, cannot connect to remote server(451 4.4.0 Socket error ConnectionReset)’
10/13/2021 4:22:34 PM - Server at example.com (xxx.yyy.zzz.163) returned ‘450 4.4.317 Cannot connect to remote server [Message=451 4.4.0 Socket error ConnectionReset] [LastAttemptedServerName=example.com] [LastAttemptedIP=xxx.yyy.zzz.163:25] [example.eop-nam12.prod.protection.outlook.com](451 4.4.0 Socket error ConnectionReset)’

Original message headers:

Received: from example.namprd11.prod.outlook.com (xxxx:yyyy:a03:b4::21)
by example.namprd11.prod.outlook.com (xxxx:yyyy:a03:f8::11) with
Microsoft SMTP Server (version=TLS1_2,
cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4608.15; Wed, 13 Oct
2021 03:11:53 +0000
ARC-Seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none;
b=gFLBtnflhEUpfcen6fKp2gaxOH15Fvlxogi2kclBMYJhSNbjg95lT8QFRO+UUZC/zH7s+id+Hcxq6OqtHh9Y/RLLWqKjaOZ12xVK0/8vsac3r7sVyGG7sSoB4ZuWbjGGUmtk78zhY9QjdQPZVcTYaDEmDQbY8uhKBL+7duTLlpO3eZW5GvR86rEIoN8jUJp77d6QQR2trlyXqCSwEe59Hn+MS9/3jzFs0ky/tVEh1gUV9caMWh2BHYEn7lcMwMnoV6YHh/jENq31jHndrjS2Of7FICGbr0Eu6iicN2npwzY50sf8lGq6HAcXU9hMGvrOqy8Ci0t9M7zyVKN8PDyQsQ==
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=4qNxxT0bvj1VwRu/5YxkBRshn152flq9Jpqxd++d/7Y=;
b=ivfoKOUYCIUSTkeZHGED+fnUfSkUZxAMpIqhKboodj+WWjHSv87bRkViKCWMTY4Fwhf4v/pdU93SKhqggMuK+mgLSR4o0sTfpmfW2ntTfPpvoqOp3c/+e4Ds6jrocfUscgiVY2A/8n/+3SQMKpbuBr/q447+csvoDpBHLyXiLUMAVp+AG59SQTdWJGWxetrVETG1aKgWtUZrbxjxAHyPFx3KfcWEyTmTgNALw7erzZ+dWF/vBE1VMY1ba0ENqw+LQhuDX8j3n80BNqfEcA4MIH81sWh6b0psOT9vOKoVbd+QLo94mG0rQt99VuFWO1aJBbTH4VcazRP4AQ3+bGlmAg==
ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass
smtp.mailfrom=example.com; dmarc=pass action=none header.from=example.com;
dkim=pass header.d=example.com; arc=none
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
d=example.onmicrosoft.com; s=selector2-example-onmicrosoft-com;
h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck;
bh=4qNxxT0bvj1VwRu/5YxkBRshn152flq9Jpqxd++d/7Y=;
b=NBC4nesUgwixI6/lOOi5caFpky+N4yWxq3k2BuhAZB/gYgZK4nzm/jxQn8Enr1V8h7RF50rCiZPUqTdifblfZkUg5TNttyHGmxO5fjn5vYFLoyP2qWHxGHf1p5j2VhRqzqdHmiGu50J2yWnQCn/XT4pkQT30jqEj2wiFVGRreoM=
Received: from example2.namprd11.prod.outlook.com (xxxx:yyyy:a03:2ad::14)
by example.namprd11.prod.outlook.com (xxxx:yyyy:a03:b4::21) with
Microsoft SMTP Server (version=TLS1_2,
cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4587.18; Tue, 12 Oct
2021 16:27:30 +0000
Received: from example2.namprd11.prod.outlook.com
([xxxx::yyyy:82ac:bef9:609c]) by example2.namprd11.prod.outlook.com
([xxxx::yyyy:82ac:bef9:609c%6]) with mapi id 15.20.4587.026; Tue, 12 Oct 2021
16:27:30 +0000
From: First Last fname@example.com
To: “reciepient@example.comreciepient@example.com
CC: “xxx@example.comxxx@example.com
Subject: email subject here
Thread-Topic: email subject here
Thread-Index: AQHXv4U3rrvQuLjuyE6Hw8DbZvWdCw==
Date: Tue, 12 Oct 2021 16:27:30 +0000
Message-ID: example2943732845882FABC52E0D8B69@example2.namprd11.prod.outlook.com
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
suggested_attachment_session_id: 5ea385f1-0b28-519a-27de-5e0a4bfcfbb3
authentication-results: example.com; dkim=none (message not signed)
header.d=none;example.com; dmarc=none action=none
header.from=example.com;
x-ms-publictraffictype: Email
x-ms-office365-filtering-correlation-id: 330c48b5-7a5b-431d-b01c-08d98d9d2fe5
x-ms-traffictypediagnostic: example:|example:
x-ms-exchange-atpmessageproperties: SA|SL
x-microsoft-antispam-prvs: exampleD172896FB93810003494D8B69@example.namprd11.prod.outlook.com
x-ms-oob-tlc-oobclassifiers: OLM:9508;
x-ms-exchange-senderadcheck: 1
x-ms-exchange-antispam-relay: 0
x-microsoft-antispam: BCL:0;
x-microsoft-antispam-message-info: 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
x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:example2.namprd11.prod.outlook.com;PTR:;CAT:NONE;SFS:(366004)(66946007)(6506007)(166002)(91956017)(76116006)(508600001)(75432002)(786003)(4326008)(9686003)(66446008)(66556008)(64756008)(66476007)(55016002)(7696005)(316002)(38070700005)(8676002)(186003)(26005)(8936002)(52536014)(19627405001)(5660300002)(38100700002)(86362001)(296002)(33656002)(2906002)(71200400001)(122000001)(6916009);DIR:OUT;SFP:1102;
x-ms-exchange-antispam-messagedata-chunkcount: 1
x-ms-exchange-antispam-messagedata-0: =?iso-8859-1?Q?gJ2EZ4o/O+IwcrHtdwy+eIItkOsBd90FM0cgvTUHtv/kOytlmDbqY7KsuW?=
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x-ms-exchange-transport-forked: True
Content-Type: multipart/alternative;
boundary=“000_example2943732845882FABC52E0D8B69example2namp
MIME-Version: 1.0
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-AuthSource: example2.namprd11.prod.outlook.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 330c48b5-7a5b-431d-b01c-08d98d9d2fe5
X-MS-Exchange-CrossTenant-originalarrivaltime: 12 Oct 2021 16:27:30.1275
(UTC)
X-MS-Exchange-CrossTenant-fromentityheader: Hosted
X-MS-Exchange-CrossTenant-id: 83b02c92-5f26-48ed-9e5b-6c2fca46a8e6
X-MS-Exchange-CrossTenant-mailboxtype: HOSTED
X-MS-Exchange-CrossTenant-userprincipalname: mTKWCj9EBHofj4J0cgEjuB21KbpmKX+qp+qEvRhJ9ypaYRVk01EVtlwhuaRTbIhhzZcRzHvUb9Xbq+45FlSOgQ==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: example
Return-Path: fname@example.com
X-OriginatorOrg: example.com

I also partially suspected the recent update to postfix that I promptly applied but I could not verify that to be the root cause of the issue. Aggressive spam blocking with the new update could be a problem, for example, but how do I confirm that’s the case?

This has been happening at least since late September/early October. Any ideas or suggestions from the community to help diagnose what might be wrong would be really helpful.