Gmailへの送信エラー

事象

Gmailへの送信エラー（スターサーバーから送信）

———- Forwarded message ———
From: Mail Delivery System MAILER-DAEMON@mailsender115.xserver.jp
Date: 2024年7月9日(火) 11:08
Subject: Undelivered Mail Returned to Sender
To: <「送信元メルアド」>

This is the mail system at host mailsender115.xserver.jp.

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

<「送信先メルアド」>: host gmail-smtp-in.l.google.com[「gmailのIP」]
said: 「said」 Your email has been blocked because the sender is
unauthenticated. 550-5.7.26 Gmail requires all senders to authenticate with
either SPF or DKIM. 550-5.7.26 550-5.7.26 Authentication results:
550-5.7.26 DKIM = did not pass 550-5.7.26 SPF [「送信元ドメイン」] with ip:
[183.181.99.206] = did not pass 550-5.7.26 550-5.7.26 For instructions on
setting up authentication, go to 550 5.7.26
https://support.google.com/mail/answer/81126#authentication
41be03b00d2f7-77d5fc3b7cesi976114a12.494 – gsmtp (in reply to end of DATA
command)