The reason why the mail I sent via Postfix is returned as an error.

The email I sent via Postfix shows the error below.What can be considered as the cause?
I'm looking into it myself, but I don't know the cause.
The destination address is not Gmail.

Hi.This is the mail program at ns.netyou.jp.
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.

<***@g mail.com>: host gmail-smtp-in.l.google.com [74.23.23.27]
    said —550-5.7.26 This message does not have authentication information or
    fails to 550-5.7.26 pass authentication checks. To best protect your users
    from spam, the 550-5.7.26 message has been blocked. Please visit 550-5.7.26
    https://support.google.com/mail/answer/81126#authentication for more 550
    5.7.26 information.t71-20020a63814a00000000b0039d7613ebaesi1450017 pgd.97-
    gsmtp (in reply to end of DATA command)

Reporting-MTA: dns; mail02-you-outgoing.ns.netyou.jp
X-Postfix-Queue-ID: 6DA79E105BF
X-Postfix-Sender: rfc822;***
Arrival-Date:Tue, 12 Apr 2022 11:54:09 + 0900 (JST)

Final-Recipient: rfc822;***@g mail.com
Action—Failed
Status: 5.7.26
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.26 This message does not have authentication
    information or failures to 550-5.7.26 pass authentication checks.Tobest
    protect your users from spam, the 550-5.7.26 message has been blocked.
    Please visit 550-5.7.26
    https://support.google.com/mail/answer/81126#authentication for more 550
    5.7.26 information.t71-20020a63814a00000000b0039d7613ebaesi1450017 pgd.97-
    gsmtp

gmail postfix

2022-09-30 17:49

2 Answers

The ns.netyou.jp server sends an error message to gmail.com, so it's a problem between the ns.netyou.jp server and the gmail.com server.
If this error indicates that the email sent to the netyou.jp domain email address, the destination user may have set up the forwarding settings for Gmail.

2022-09-30 17:49

To best protect your users from spam,

Gmail treats the email I sent as spam.
For 550-5.7.26 error codes, see
Gmail SMTP errors and codes - Google Workspace Administrator Help
According to this, it was not approved by the DMARC policy.
If you haven't experienced any problems in the past, your Gmail receiving policy may have recently changed.You may need to change the source settings by referring to the following article:
Use DMARC to Prevent Spoofing and Spam - Google Workspace Administrator Help

2022-09-30 17:49

If you have any answers or tips

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