1. whois

メール認証

Email authentication requirements & guidelines

We require that you set up these email authentication methods for your domain:

    All senders: SPF or DKIM
    Bulk senders: SPF, DKIM, and DMARC

Authenticated messages:

    Help protect recipients from malicious messages, such as spoofing and phishing messages.
    Help protect you and your organization from being impersonated. 
    Are less likely to be rejected or marked as spam by Gmail.

Set up email authentication for each of your sending domains at your domain provider. You can use instructions Google provides and our domain provider's email authentication support information.

To verify messages are authenticated, Google performs checks on messages sent to Gmail accounts. To improve email delivery, we recommend that you always set up SPF, DKIM, and DMARC for your domains. Make sure you're meeting the minimum authentication requirements described on this page. Messages that aren’t authenticated with these methods might be marked as spam or rejected with a 5.7.26 error. }}}

2. history

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