I don't remember this happening in the past nor have I made changes.

Here's the bounce message:

This is the mail system at host mail.lifeassetsllc.com.

I'm sorry to have to inform you that your message could not
be delivered to one or more recipients. It's attached below.

For further assistance, please send mail to postmaster.

If you do so, please include this problem report. You can
delete your own text from the attached returned message.

                   The mail system

<MY Mom's Email address@gmail.com>: host
    gmail-smtp-in.l.google.com[2607:f8b0:4023:c0d::1b] said: 550-5.7.25
    [2607:f130:0:f7:216:3eff:fe7c:9ec5] The IP address sending this 550-5.7.25
    message does not have a PTR record setup, or the corresponding 550-5.7.25
    forward DNS entry does not point to the sending IP. As a policy, 550-5.7.25
    Gmail does not accept messages from IPs with missing PTR records.
    550-5.7.25 For more information, go to 550-5.7.25
    https://support.google.com/mail/answer/ … -practices  550-5.7.25 To
    learn more about Gmail's sender policy, go to 550 5.7.25
    https://support.google.com/mail/answer/81126.
    c16-20020a63d510000000b005dc89319b58si10225642pgg.682 - gsmtp (in reply to
    end of DATA command)

along with an attachment to the email:

Return-Path: <myemail@lifemodelsllc.com>
Received: from mail.lifeassetsllc.com (mail.lifeassetsllc.com [127.0.0.1])
    by mail.lifeassetsllc.com (Postfix) with ESMTP id 4VPG2G66Xkz981
    for <Mom's Email@gmail.com>; Tue, 23 Apr 2024 17:48:06 -0400 (EDT)
Authentication-Results: mail.lifeassetsllc.com (amavisd-new);
    dkim=pass (2048-bit key) reason="pass (just generated, assumed good)"
    header.d=lifemodelsllc.com
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=
    lifemodelsllc.com; h=x-mailer:to:message-id:subject:date
    :mime-version:from:content-transfer-encoding:content-type; s=
    dkim; t=1713908886; x=1716500887; bh=LBnQoLnGzd7IzsBFwBpFTRcEKeZ
    5Srpx1hUgwsSfUns=; b=LipMWy2PMA3dWem0EqRaA90h+Za7NsajUv56ImeczuB
    Bk9lOTjvPLz/EPlo+iSf5IbwoG1WmF8IC2tcq+M76K+oBvf2Lxg4Bd57bESGGbmg
    h5+nuYpN14z9tIJpK2EavsMWidtTFrvbz/bkcENHD6MQr3KJhVH8l250ieKpHe6b
    LZM2+4meAsZ2+dxlrEQyoESIXAvsw4fcyF8nW905ALo/61Ht7gYUTyoEgbbPT4Lf
    sc1WowHCJcLGg6V26DGIuBS1ai6nmQRLVxNCTNVI+RtiUKJ1Do44nFlB1q10csCO
    xGTnNgtvOOvJlV4u2+ThAi1aVewZVPYv7CDfWXs2y6g==
X-Virus-Scanned: amavisd-new at mail.lifeassetsllc.com
Received: from mail.lifeassetsllc.com ([127.0.0.1])
    by mail.lifeassetsllc.com (mail.lifeassetsllc.com [127.0.0.1]) (amavisd-new, port 10026)
    with ESMTP id zxcdGlLsCAie for <mom's email@gmail.com>;
    Tue, 23 Apr 2024 17:48:06 -0400 (EDT)
Received: from smtpclient.apple (pool-173-72-11-197.cmdnnj.fios.verizon.net [173.72.11.197])
    by mail.lifeassetsllc.com (Postfix) with ESMTPSA id 4VPG2G0PCrzB11
    for <my mom@gmail.com>; Tue, 23 Apr 2024 17:48:06 -0400 (EDT)
Content-Type: multipart/alternative; boundary=Apple-Mail-DB29DAB6-0059-46BC-B499-7BACC19EA598
Content-Transfer-Encoding: 7bit
From: "Me" <my email@lifemodelsllc.com>
Mime-Version: 1.0 (1.0)
Date: Tue, 23 Apr 2024 17:48:04 -0400
Subject: =?utf-8?Q?Screenshot_2024-04-23_at_5.47.45=E2=80=AFPM?=
Message-Id: <84B5D76A-1DC3-4ED2-AFF6-C2601C999919@lifemodelsllc.com>
To: Mom <mom's email@gmail.com>
X-Mailer: iPhone Mail (21E236)

The reverse DNS and other records are/were set by my hosting company.  What, per the bounce, should they be set to?  Not sure why this error popped up, and I certainly can't debug how to fix it.

Thanks everyone.

Andrew