Issue Notifications Email and 550 error

[JuanCar]

Hello
I have configured my email as name@mydomain.com in admin account.
As second email (for recovering password) I have set myaccount@gmail.com
Mail has DKIM SPF activated.
By default, Plesk sends its notifications to the second email (myaccount@gmail.com), not the admin email.
And I get an email from my qmail-send program about the 550 error.
Reading these error mails I see the return path of notifications mails are the same as target mail: myaccount@gmail.com (my second email, not admin email)
I think the issue can be in the value of this return path, but I can not find where set this value in Plesk config.
Of course I can send emails to gmail from my server mail (name@mydomain.com) without any problem.
Where can be the problem and how to fix it?
Thanks
This is a copy of mail telling about the 550 error:
Hi. This is the qmail-send program at mydomain.com.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.
<myaccount@gmail.com>:

108.177.14.27 failed after I sent the message.
Remote host said: 550-5.7.26 This mail is unauthenticated, which poses a security risk to the
550-5.7.26 sender and Gmail users, and has been blocked. The sender must
550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,
550-5.7.26 DKIM checks did not pass and SPF check for [gmail.com] did not pass
550-5.7.26 with ip: [ip of my server]. The sender should visit

550-5.7.26 Prevent mail to Gmail users from being blocked or sent to spam - Gmail Help for
550 5.7.26 instructions on setting up authentication. h23-20020a2e9017000000b002a8e5bf9920si1890015ljg.583 - gsmtp

--- Below this line is a copy of the message.

Return-Path: <myaccount@gmail.com>
Received: (qmail 13776 invoked by uid 997); 22 Jun 2023 05:18:02 +0200
Message-ID: <20230622031802.13774.qmail@mydomain.com>

To: =?UTF-8?Q?My Name in Gmail?= <myaccount@gmail.com>

Subject: =?UTF-8?Q?<maydomain.com>=20WordPress=20Updates=20Digest?=

Date: Thu, 22 Jun 2023 05:18:02 +0200

From: =?UTF-8?Q?My Name in Gmail?= <myaccount@gmail.com>

Sender: <myaccount@gmail.com>

Reply-To: =?UTF-8?Q?My Name in Gmail?= <myaccount@gmail.com>

X-Mailer: =?UTF-8?Q?PHP/8.2.6?=

MIME-Version: 1.0

Content-Type: text/html; charset="utf-8"

Content-Transfer-Encoding: base64

X-PPP-Message-ID:

<168740388270.13767.8648303835598941771@localhost.localdomain>

X-PPP-Vhost: localhost.localdomain

And follow the content of message coded as base64

 

[mariano_loo]

Hello... I am experiencing the same issue with all my Gmail account users on my server.
50-5.7.26 This mail is unauthenticated, which poses a security risk to the
550-5.7.26 sender and Gmail users, and has been blocked. The sender must
550-5.7.26 authenticate with at least one of SPF or DKIM. For this message,

The problem started recently as users complaining
DKIM
Passes on mxtoolbox.com,
Fails on dkimvalidator.com DKIM or DK signature exists, but is not valid, Validating Signature result = fail Details: bad RSA signature
Fails on toolbox.googleapps.com/ Invalid format of DKIM record

All other domain emails like Outlook and Yahoo are working fine emails get delivered.

Any suggestions???