Secretary can't send messages to members or officers lists

Hello! 
Our secretary's email is Naomi@RoseButterfly.com. She uses Outlook on a MacBook, and sends emails from a private server.

On Aug 8-9, she tried to email our members list, members-1713@toastmastersclub.org -- no attachments, just a message.
On 8/11/23 she got an error email "multiple delivery attempts failed" (full text is below)
On 8/16/23 I watched her try to email our members & officers lists; both tries failed, ie, I didn't get her test emails, and she got error messages like the one below 1-2 days later. 

Can you help us resolve or advise next steps? I saw several posts like mine that suggest her IP might be blocked.

Thank you!
Sandy Pon
Presidents Club Toastmasters #1713
presidentsclub.toastmastersclubs.org/

===

> This message was created automatically by mail delivery software.
>
> A message that you sent could not be delivered to one or more of
> its recipients. This is a permanent error.
>
> The following address failed:
>
>    members-1713@toastmastersclubs.org:
>        multiple delivery attempts failed
>
> --- The header of the original message is following. ---
>
> Received: from smtpclient.apple ([76.105.98.172]) by mrelay.perfora.net
> (mreueus002 [74.208.5.2]) with ESMTPSA (Nemesis) id 0LfkxY-1q27VB2Htq-00pKIp
> for <members-1713@toastmastersclubs.org>; Fri, 11 Aug 2023 04:03:47 +0200
> From: Naomi Morad <Naomi@RoseButterfly.com>
> Content-Type: text/plain;
>        charset=utf-8
> Content-Transfer-Encoding: quoted-printable
> Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.600.7\))
> Subject: Table Topics Theme for August 16th
> Message-Id: <8D45B55C-7AEB-4601-B3BB-4C1730CAFA75@RoseButterfly.com>
> Date: Thu, 10 Aug 2023 22:03:36 -0400
> To: members-1713@toastmastersclubs.org
> X-Mailer: Apple Mail (2.3731.600.7)
> X-Provags-ID: V03:K1:VxlLFGqqLI0qT/QA9jkxW5+xZy1AJ/HaQVcbOqt14H29mnvfNo+
> x/i+TGw6VemuxT+njNps0zTFN9zJX9ax0+oUH/dmXY2Bkj2TZWjS4cWO6KjWDdmr0ci6XZl
> zGFa8moeoszvXIOsOLwDQNWOONrLVkBb1XzJyJijjSzcUalsMmdSjG0Os8xt5K0yEeHcgGb
> n6QINSnp1l02BKC8tiOmQ==
> Reporting-MTA:dns;perfora.net
> Arrival-Date:Fri, 11 Aug 2023 04:03:47 +0200
>
> Final-Recipient:rfc822;members-1713@toastmastersclubs.org
> Action:failed
> Status:5.0.0
> Final-Log-ID:0LfkxY-1q27VB2Htq-00pKIp

Please have her try and send an email now.

Hi Brian,
Issue resolved! Naomi now can send emails to both group lists again. Thanks for your quick response -- and all the work you and your FTH teammates do to provide us this highly helpful service! We appreciate you.
You can close this "ticket" or thread now. Thanks!
Best regards,
Sandy