Blacklist on bell.net

Emails from FreeToastHost to all members with bell.net or sympatico.ca email addresses bounced and these addresses and have now been removed from the FreeToastHost server. Emails from my personal email do not bounce on these addresses.
Have other clubs this problem, too? How am I going to fix this?
I have instructed the memebers to follow these instructions:
support.bell.ca/internet/email/i-can-t-r...-sender-in-bell-mail
I suppose the address to be whitelisted is server@toastmastersclubs.org. Am I correct?
Once they have sucessfully done this, how can I check if the problem has been solved/ Shall I go ahead and reinstate their email addresses at the club website?

Sample header of bouncing email:

From MAILER-DAEMON@toastmastersclubs.org Tue Nov 23 09:49:33 2021
Received: from localhost (localhost)
by toastmastersclubs.org (8.14.4/8.14.4) id 1AN9j1ce015716;
Tue, 23 Nov 2021 09:49:33 GMT
Date: Tue, 23 Nov 2021 09:49:33 GMT
From: Mail Delivery Subsystem <MAILER-DAEMON@toastmastersclubs.org>
Message-Id: <202111230949.1AN9j1ce015716@toastmastersclubs.org>
To: <server@toastmastersclubs.org>
MIME-Version: 1.0
Content-Type: multipart/report; report-type=delivery-status;
boundary="1AN9j1ce015716.1637660973/toastmastersclubs.org"
Subject: Returned mail: see transcript for details
Auto-Submitted: auto-generated (failure)

This is a MIME-encapsulated message

--1AN9j1ce015716.1637660973/toastmastersclubs.org

The original message was received at Sun, 21 Nov 2021 23:58:15 GMT
from toastmastersclubs.org [127.0.0.1]

---

The following addresses had permanent fatal errors

---

<lindacucca@bell.net>

---

Transcript of session follows

---

554 5.0.0 Service unavailable

--1AN9j1ce015716.1637660973/toastmastersclubs.org
Content-Type: message/delivery-status

Reporting-MTA: dns; toastmastersclubs.org
Arrival-Date: Sun, 21 Nov 2021 23:58:15 GMT

Final-Recipient: RFC822; lindacucca@bell.net
Action: failed
Status: 5.5.0
Remote-MTA: DNS; mxmta.owm.bell.net
Last-Attempt-Date: Tue, 23 Nov 2021 09:49:33 GMT

--1AN9j1ce015716.1637660973/toastmastersclubs.org
Content-Type: message/rfc822

Return-Path: <server@toastmastersclubs.org>
Received: from localhost.localdomain (toastmastersclubs.org [127.0.0.1])
by toastmastersclubs.org (8.14.4/8.14.4) with ESMTP id 1ALNw9qa012785
for <lindacucca@bell.net>; Sun, 21 Nov 2021 23:58:15 GMT
Message-Id: <202111212358.1ALNw9qa012785@toastmastersclubs.org>
Received: from st43p00im-ztdg10063201.me.com (st43p00im-ztdg10063201.me.com [17.58.63.182])
by toastmastersclubs.org (8.14.4/8.14.4) with ESMTP id 1ALNw6Mc012764
(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO)
for <members-4468@toastmastersclubs.org>; Sun, 21 Nov 2021 23:58:07 GMT
Received: from smtpclient.apple (unknown [144.172.129.247])
by st43p00im-ztdg10063201.me.com (Postfix) with ESMTPSA id 22EC354055D
for <members-4468@toastmastersclubs.org>; Sun, 21 Nov 2021 23:58:06 +0000 (UTC)
Content-Type: multipart/alternative;
boundary="Apple-Mail=_1836E1E6-01A2-4D48-A985-CB00E551FA3B"
Mime-Version: 1.0 (Mac OS X Mail 15.0 \(3693.20.0.1.32\))
Subject: Minutes of Meeting #1246
Date: Sun, 21 Nov 2021 18:58:04 -0500
X-Mailer: Apple Mail (2.3693.20.0.1.32)
X-Proofpoint-Virus-Version: =?UTF-8?Q?vendor=3Dfsecure_engine=3D1.1.170-22c6f66c430a71ce266a39bfe25bc?=
=?UTF-8?Q?2903e8d5c8f:6.0.425,18.0.790,17.0.607.475.0000000_definitions?=
=?UTF-8?Q?=3D2021-11-21=5F12:2021-11-17=5F01,2021-11-21=5F12,2020-04-07?=
=?UTF-8?Q?=5F01_signatures=3D0?=
X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 clxscore=1015 mlxlogscore=975
malwarescore=0 suspectscore=0 spamscore=0 bulkscore=0 adultscore=0
mlxscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1
engine=8.12.0-2009150000 definitions=main-2111210146
X-Spam-Status: No, score=-0.7 required=5.0 tests=FREEMAIL_FROM,HTML_MESSAGE,
RCVD_IN_DNSWL_LOW,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,
SPF_PASS,T_FREEMAIL_DOC_PDF autolearn=unavailable autolearn_force=no
version=3.4.3
X-Spam-Checker-Version: SpamAssassin 3.4.3 (2019-12-06) on
toastmastersclubs.org
From: "Toastmasters Club 4468 on behalf of Andreas Schwab, DTM"
<server@toastmastersclubs.org>
X-Loop: server@toastmastersclubs.org
Sender: andreas.j.schwab@icloud.com
Errors-To: andreas.j.schwab@icloud.com
Reply-To: secretary-4468@toastmastersclubs.org
Content-Transfer-Encoding: 7bit
To: "members-4468@toastmastersclubs.org"
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed; d=toastmastersclubs.org;

server@toastmastersclubs.org and agenda@toastmastersclubs.org should be added to your contact and white list.