Postfix Gmail Bounce: This message does not have authentication information or fails to 550-5.7.26 pass authentication checks.
If you try to send email from your server using postfix without the correct SPF DNS record, it will most likely be rejected by Gmail, Outlook and other major email providers.
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How to enable 2-Step Verification for your Google Account
How to set up 2-step verification (2FA) to add an extra layer of security to your Google Account or G Suite, and the different verification methods available.
