Email error for donors with address xxxxxx@t-online.de

It's the second time my server can't send emails to donors whose email is xxxxxx@t-online.de I get the following error:

This is the mail system at host mo576.mail-out.ovh.net.

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

<xxxxx@t-online.de>: host mx02.t-online.de[194.25.134.9] said: 559 5.1.9
(DKIM reject DKIMr) Missing, invalid or non-matching DKIM signature (in
reply to end of DATA command)


Reporting-MTA: dns; mo576.mail-out.ovh.net
X-Postfix-Queue-ID: 4TZFt02WPSz1SRh
X-Postfix-Sender: rfc822; jl@jjazzlab.org
Arrival-Date: Tue, 13 Feb 2024 22:11:52 +0000 (UTC)

Final-Recipient: rfc822; xxxx@t-online.de
Original-Recipient: rfc822;xxxx@t-online.de
Action: failed
Status: 5.1.9
Remote-MTA: dns; mx02.t-online.de
Diagnostic-Code: smtp; 559 5.1.9 (DKIM reject DKIMr) Missing, invalid or
non-matching DKIM signature


ForwardedMessage.eml
Subject:
Re: Did not receive unlock code after 3 hrs
From:
JL <jl@jjazzlab.org>
Date:
13/02/2024, 23:11
To:
xxxx@t-online.de

Thanks for the donation.

Did you check your spam folder ? Anyway, find below a copy of your code:

code: xxxxxx
email: xxxxx@t-online.de

Greetings
Jerome

If you have such an email address, try sending me an email from a different one, such as gmail etc.